A long-term growth stable Halomonas sp. deleted with multiple transposases guided by its metabolic network model Halo-ecGEM.

Microbial instability is a common problem during bio-production based on microbial hosts. Halomonas bluephagenesis has been developed as a chassis for next generation industrial biotechnology (NGIB) under open and unsterile conditions. However, the hidden genomic information and peculiar metabolism have significantly hampered its deep exploitation for cell-factory engineering. Based on the freshly completed genome sequence of H. bluephagenesis TD01, which reveals 1889 biological process-associated genes grouped into 84 GO-slim terms. An enzyme constrained genome-scale metabolic model Halo-ecGEM was constructed, which showed strong ability to simulate fed-batch fermentations. A visible salt-stress responsive landscape was achieved by combining GO-slim term enrichment and CVT-based omics profiling, demonstrating that cells deploy most of the protein resources by force to support the essential activity of translation and protein metabolism when exposed to salt stress. Under the guidance of Halo-ecGEM, eight transposases were deleted, leading to a significantly enhanced stability for its growth and bioproduction of various polyhydroxyalkanoates (PHA) including 3-hydroxybutyrate (3HB) homopolymer PHB, 3HB and 3-hydroxyvalerate (3HV) copolymer PHBV, as well as 3HB and 4-hydroxyvalerate (4HB) copolymer P34HB. This study sheds new light on the metabolic characteristics and stress-response landscape of H. bluephagenesis, achieving for the first time to construct a long-term growth stable chassis for industrial applications. For the first time, it was demonstrated that genome encoded transposons are the reason for microbial instability during growth in flasks and fermentors.

Pulsed light processing of sugarcane juice: quality evaluation and microbial load assessment.

BACKGROUND: Freshly extracted sugarcane juice is an ideal substrate for microbial fermentation and browning reactions. The present study is the first report on the potential of pulsed light (PL) processing in improving microbial stability with the retention of major bioactive. PL processing at different levels of voltage (2.1-2.7 kV) and number of pulses (100-200) was explored. The present study aimed to investigate the impact of PL processing on the quality of sugarcane juice, bioactive composition and microbial load. RESULTS: The microbial load, such as aerobic mesophiles, yeast and mold, and total coliform, was reduced to below 1 log colony-forming units mL-1 in juice samples subjected to intense PL treatment at 2.7 kV. The maximum value of the total color difference of the sugarcane juice was below 4.0, even at extreme levels of PL process parameters. In comparison with the unprocessed juice, the reduction in total phenols (Folin ciocalteu reagent assay) and the total antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay) was limited to 6% and 16.7%, respectively, when treated at 2.7 kV/200 pulses. The pH and total soluble solids of the juice remained unaffected in all the processed samples. Among the process parameters considered, the treatment voltage was found to significantly affect the quality parameters and microbial load. CONCLUSION: PL processing at 2.1 kV/170 pulses gave an optimally processed juice with a microbial load below the permissible limit and desirability value of 0.77. The results suggest that the PL treatment is effective for enhancing the microbial stability and maintaining the bioactive components of the sugarcane juice. Furthermore, the outcomes from the present study are expected to pave the way for further in-depth investigation of the effect of PL treatment on the critical quality attributes and shelf life of sugarcane juice. The technology will be useful for adoption by different stakeholders, including manufacturers and retailers in the food processing sector. © 2024 Society of Chemical Industry.

Liming improves the stability of soil microbial community structures against the application of digestate made from dairy wastes.

Lime is used to reduce soil acidification in agricultural soils. However, its effects on the soil microbial community are not well understood. Additionally, the soil microbial community is known to be influenced by fertilizers. However, the question remains whether liming influences the magnitude of fertilizers' impact on soil microbial communities. Therefore, an incubation experiment was performed to understand the effect of lime application (pH = 6.5 and 5.5 for the soils with and without lime, respectively) and fertilizer (digestate, urea and control) on the soil microbial community structures, stability and gene functions. Soils were sampled weekly after the application of fertilizers for a month. For microbial community analysis, DNA was extracted and sequenced targeting 16 S rRNA region. For gene abundances i.e 16 S rRNA, ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB), nitrous oxide reductase (nosZ) and nitrite reductase (nirS) quantitative PCR was conducted. In results, the relative abundance of Actinobacteria was influenced more strongly by digestate in lime soils, while Alphaproteobacteria was influenced more strongly by digestate in the no lime soil. In NL treatments, digestate had a significant effect on more operational taxonomic units (146) compared to lime (127), indicating that lime application increased soil microbial community's stability. Liming and fertilizer had a significant effect on 16 S rRNA gene copy numbers with the highest values observed in lime plus digestate treatments. Soil pH had a significant effect on AOA, nosZ and nirS gene copy numbers with the highest values observed in lime treatments. In the lime treatments digestate application had a positive impact on AOB gene copy numbers but this was not the case for soils without liming treatments. These results indicate that soil pH and fertilizer type should be taken into consideration for the management of functional gene abundance in agricultural soils.

Resilience of Soil Microbial Communities to Metals and Additional Stressors: DNA-Based Approaches for Assessing "Stress-on-Stress" Responses.

Many microbial ecology studies have demonstrated profound changes in community composition caused by environmental pollution, as well as adaptation processes allowing survival of microbes in polluted ecosystems. Soil microbial communities in polluted areas with a long-term history of contamination have been shown to maintain their function by developing metal-tolerance mechanisms. In the present work, we review recent experiments, with specific emphasis on studies that have been conducted in polluted areas with a long-term history of contamination that also applied DNA-based approaches. We evaluate how the "costs" of adaptation to metals affect the responses of metal-tolerant communities to other stress factors ("stress-on-stress"). We discuss recent studies on the stability of microbial communities, in terms of resistance and resilience to additional stressors, focusing on metal pollution as the initial stress, and discuss possible factors influencing the functional and structural stability of microbial communities towards secondary stressors. There is increasing evidence that the history of environmental conditions and disturbance regimes play central roles in responses of microbial communities towards secondary stressors.

Effect of thyme/cumin essential oils and butylated hydroxyl anisole/butylated hydroxyl toluene on physicochemical properties and oxidative/microbial stability of chicken patties.

In this study, effects of thyme/cumin essential oils (EO) and butylated hydroxyl anisole (BHA)/butylated hydroxyl toluene (BHT) on physicochemical properties and storage stability of chicken patties were compared in different storage periods (0, 3, 7, 14, 21, and 28 d). It was found that there were significant (P < 0.05) differences between physicochemical properties of patty samples treated with EO and the synthetic antioxidants. The EO showed similar performance to those of BHA and BHT in limiting TBARS values of chicken patty samples. Similarity in performance was also the case for microbial stability (total aerobic mesophilic, psychrotrophic, lactic acid, and coliform bacteria as well as molds and yeasts); namely, their effects were significant (P < 0.05). Effect of thyme EO was significant (P < 0.05) and remarkable, not allowing any coliform bacteria to grow in the samples. Given that EO were obtained from natural sources, the data suggested that the EO might be more useful than their synthetic counterparts, BHA and BHT, as additives for chicken patties to maintain oxidative/microbial stability and increase shelf life.

Urbanization reduces the stability of soil microbial community by reshaping the diversity and network complexity.

Rapid urbanization considerably alters soil environment, biodiversity, and stability of terrestrial ecosystems. Soil microbial community, a key component of global biodiversity, plays a pivotal role in ecosystem stability and is highly vulnerable to urbanization. However, effects of urbanization on the diversity, stability, and network structure of soil microbial community remain poorly understood. Herein, we investigated the diversity and stability of soil microbial communities, including bacteria, fungi, and protists, across three regions with different levels of urbanization-urban, suburb, and ecoregion-using high-throughput sequencing techniques. Our results revealed that urbanization led to a notable decrease in the alpha diversity of soil microbial community, causing a significant reduction in soil stability, as assessed by the average variation degree (AVD). The loss of stability was linked to the diminished alpha diversity of the soil fungal and protistan communities, along with weakened interactions among bacteria, fungi, and protists. Notably, the majority of keystone species identified through network analysis were classified as bacteria (Proteobacteria) and displayed a strong positive correlation with the environmental factors influencing AVD. This highlights that the variability of bacteria and the immutability of fungi and protists are important to sustain soil microbial stability. Furthermore, structural equation models indicated that protistan diversity primarily drove soil microbial stability across all regions studied. In the suburban and ecoregion areas, soil microbial stability was directly influenced by the soil properties, bacterial diversity, and keystone species, as well as indirectly affected by heavy metals. These results underscore how urbanization can reduce the stability of soil microbial community via declined diversity and network complexity, whereas the establishment of ecoregions maybe contribute to preserve the diversity and stability of soil microbial community.

Various cold storage-backslopping cycles show the robustness of Limosilactobacillus fermentum IMDO 130101 as starter culture for Type 3 sourdough production.

Type 3 sourdoughs, which are starter culture-initiated and subsequently backslopped, are less studied than other sourdough types. Yet, they can serve as a model to assess how competitive starter culture strains for sourdough production are and how the microbial composition of such sourdoughs may evolve over time. In the present study, Limosilactobacillus fermentum IMDO 130101 was used to produce Type 3 sourdoughs, prepared from wheat and wholemeal wheat flours. Therefore, an initial fermentation of the flour-water mixture was performed at 30 °C for 48 h. This was followed by cold storage-backslopping cycles, consisting of refreshments (50 %, v/v), fermentation steps of 16 h, and storage at 4 °C each week, every three weeks, and every six weeks. The microbial dynamics (culture-dependent and -independent approaches) and metabolite dynamics were measured. In all sourdoughs produced, starter culture strain monitoring, following an amplicon sequence variant approach, showed that Liml. fermentum IMDO 130101 prevailed during one month when the sourdoughs were refreshed each week, during 24 weeks when the sourdoughs were refreshed every three weeks, and during 12 weeks when the sourdoughs were refreshed every six weeks. This suggested the competitiveness and robustness of Liml. fermentum IMDO 130101 for a considerable duration but also showed that the strain is prone to microbial interference. For instance, Levilactobacillus brevis and Pediococcus spp. prevailed upon further cold storage and backslopping. Also, although no yeasts were inoculated into the flour-water mixtures, Kazachstania unispora, Torulaspora delbrueckii, and Wickerhamomyces anomalus were the main yeast species found. They appeared after several weeks of storage and backslopping, which however indicated the importance of an interplay between LAB and yeast species in sourdoughs. The main differences among the mature sourdoughs obtained could be explained by the different flours used, the refreshment conditions applied, and the sampling time (before and after backslopping). Finally, the metabolite quantifications revealed continued metabolite production during the cold storage periods, which may impact the sourdough properties and those of the breads made thereof.

Gut microbial stability in older Japanese populations: insights from the Mykinso cohort.

Gut microbiota imbalance plays an important role in the pathogenesis of various diseases. Here, we determined microbe-microbe interactions and gut microbiome stability in a Japanese population with varying body mass indices (BMIs) and enterotypes. Using 16S ribosomal RNA gene sequencing, we analyzed gut microbial data from fecal samples obtained from 3,365 older Japanese individuals. The individuals were divided into lean, normal, and obese groups based on their BMIs. They were further categorized according to their gut microbiota enterotypes: Bacteroides (enterotype B), Prevotella (enterotype P), and Ruminococcus (enterotype R). We obtained data on different host factors, such as age, BMI, and disease status, using a survey questionnaire evaluated by the Mykinso gut microbiome testing service. Subsequently, we evaluated the co-occurrence network. Individual differences in BMI were associated with differences in co-occurrence networks. By exploring the network topology based on BMI status, we observed that the network density was lower in the lean group than that in the normal group. Furthermore, a simulation-based stability analysis revealed a lower resistance index in the lean group than those in the other two groups. Our results provide insights into various microbe-microbe interactions and gut microbial stability and could aid in developing appropriate therapeutic strategies targeting gut microbiota modulation to manage frailty.

Isolation, identification, and stability of sourdough microbiota from spontaneously fermented Norwegian legumes.

Fermentation has recently been rediscovered as an attractive technique to process legumes, as it can improve the nutritional quality and value of the end product. This study investigated the dynamics and stability of the microbial communities in spontaneously fermented sourdoughs made from flours of two cultivars of faba beans and two cultivars of peas. Sourdoughs were established by the backslopping technique, and the microbial development at 22 °C and 30 °C was followed by culture dependent and culture independent methods. The utilization of substrates and formation of metabolites were also determined by high-performance liquid chromatography. A stable pH was reached in all the sourdoughs after 11-15 days of daily backslopping. Lactic acid bacteria and yeast from pH stable sourdoughs were isolated, characterized and identified. The fermentation temperature influenced the development of the microbial community and the substrate utilization during spontaneous fermentation. In the 30 °C fermentations, one species dominated (Lactiplantibacillus plantarum/pentosus), a lower pH was achieved, and the available substrates were more extensively converted. The 22 °C fermentation resulted in a more diverse microbial community (Lactiplantibacillus, Leuconostoc, Pediococcus), a higher pH, and more residual substrates were available after fermentation. Yeasts were only detected in one of the pea sourdoughs fermented at 30 °C, with Saccharomyces cerevisiae being the dominant species. Nearly all sourdoughs were depleted of maltose after 24 h fermentation cycles, and higher levels of lactic and acetic acid were detected in 30 °C fermen-tations. This research adds to our understanding of the autochthonous microbial community present in faba beans and peas as well as their natural capacity to establish themselves and ferment legume flours. These findings enhance the possibilities of utilizing and improving plant based protein sources.

Biotic interactions and environmental modifications determine symbiotic microbial diversity and stability.

Taking amphibians as island models, we examined the effects of interspecific interaction on the diversity and stability of microbial ecological. As skin area increased, the diversity and stability of skin microbes decreased, but the strength of negative interactions increased significantly. In contrast, as gut area increased, the diversity and stability of gut microbes increased, but the strength of interactions remained constant. These results indicate that microbial interactions are affected by habitat properties. When living in fluctuating environments without strong filtering, microorganisms can enhance their negative interactions with other taxa by changing the pH of their surroundings. In contrast, the pH of the gut is relatively stable, and colonized microorganisms cannot alter the gut pH and inhibit other colonizers. This study demonstrates that in the field of microbiology, diversity and stability are predominantly influenced by the intensity of interspecies interactions. The findings in this study deepen our understanding of microbial diversity and stability and provide a mechanistic link between species interactions, biodiversity, and stability in microbial ecosystems.

Shelf Life Extension and Nutritional Quality Preservation of Sour Cherries through High Pressure Processing.

The present study assessed the effectiveness of high pressure processing (HPP) for the quality maintenance of pitted sour cherries, with special regard to microbial stabilization and the maintenance of color and of chemical-nutritional properties. The HPP treatment (600 MPa for 3 min at 4 °C) was effective at minimizing the initial microbial load, which remained at negligible levels throughout 5 months of refrigerated storage. The color and total phytochemical content of sour cherries were not influenced by the HPP treatment and were maintained at levels comparable with the fresh product for 3 months of refrigerated storage. For longer storage periods, the typical red color decreased, in agreement with the content of total anthocyanins, which showed a significant decrease (up to 65% after 5 months). The antioxidant activity, measured by the ABTS and DPPH assays, was not affected by the HPP treatment, but slightly reduced during refrigerated storage. The study suggests that HPP may be exploited to extend the shelf life, while maintaining the fresh-like features of sour cherries, thus offering an alternative option to current preservation techniques (based on freezing or heating) commonly applied to this product.

Ecosystem multifunctionality and soil microbial communities in response to ecological restoration in an alpine degraded grassland.

Linkages between microbial communities and multiple ecosystem functions are context-dependent. However, the impacts of different restoration measures on microbial communities and ecosystem functioning remain unclear. Here, a 14-year long-term experiment was conducted using three restoration modes: planting mixed grasses (MG), planting shrub with Salix cupularis alone (SA), and planting shrub with Salix cupularis plus planting mixed grasses (SG), with an extremely degraded grassland serving as the control (CK). Our objective was to investigate how ecosystem multifunctionality and microbial communities (diversity, composition, and co-occurrence networks) respond to different restoration modes. Our results indicated that most of individual functions (i.e., soil nutrient contents, enzyme activities, and microbial biomass) in the SG treatment were significantly higher than in the CK treatment, and even higher than MG and SA treatments. Compared with the CK treatment, treatments MG, SA, and SG significantly increased the multifunctionality index on average by 0.57, 0.23 and 0.76, respectively. Random forest modeling showed that the alpha-diversity and composition of bacterial communities, rather than fungal communities, drove the ecosystem multifunctionality. Moreover, we found that both the MG and SG treatments significantly improved bacterial network stability, which exhabited stronger correlations with ecosystem multifunctionality compared to fungal network stability. In summary, this study demonstrates that planting shrub and grasses altogether is a promising restoration mode that can enhance ecosystem multifunctionality and improve microbial diversity and stability in the alpine degraded grassland.

Depth-dependent effects of tree species identity on soil microbial community characteristics and multifunctionality.

Soil microbes play key roles that support forest ecosystem functioning, while their community characteristics are strongly determined by tree species identity. However, the majority studies primarily focus on soil microorganisms in the topsoil, resulting in limited understanding of the linkages between tree species identity and the microbial communities that inhabit deep soils. Here we investigated the diversity, structure, function, and co-occurrence networks of soil bacterial and fungal communities, as well as related soil physicochemical properties, to a depth of two meters in dryland forests dominated by either Pinus tabuliformis, a native coniferous species, Robinia pseudoacacia, an exotic broadleaf and nitrogen-fixing species, or both. Tree species identity had stronger effects on soil multifunctionality and microbial community structure in the deep layers (80-200 cm) than in the top layers (0-60 cm). In addition, fungal communities were more responsive to tree species identity, whereas bacteria were more sensitive to soil depth. Tree species identity strongly influenced microbial network stability and complexity, with higher quantities in R. pseudoacacia than the other plantations, by affecting microbial composition and their associations. The increased in microbial network complexity and the relative abundance of keystone taxa enhance the soil multifunctionality of microbial productivity, sugar and chitin degradation, and nutrient availability and cycling. Meanwhile, the relative abundance of keystone taxa was more representative of soil multifunctionality than microbial diversity. Our study highlights that tree species identity significantly influences soil microbial community characteristics and multifunctionality, especially in deep soils, which will help us understand soil nutrients processed in plantation forest ecosystem and provide a reference for tree species selection in ecological restoration.

Effect of Flaxseed Oil Cake Extract on the Microbial Quality, Texture and Shelf Life of Gluten-Free Bread.

Extending the shelf life of gluten-free bread (GFB) is a challenge. Mainly due to the ingredients used and their characteristics, GFB has numerous drawbacks such as unsatisfactory texture and rapid staling beyond a low nutritional value. In the present study, flaxseed oil cake extract (FOCE) was used to replace water (25-100%) in GFB formulations in order to test FOCE's potential to reduce GFB staling and extend microbial stability. Texture (TPA test), water activity (LF NMR), acidity (pH measurements) and microbiological quality of GFBs were tested. Moreover, the content of a lignan with broad health-promoting potential, secoisolariciresinol diglucoside (SDG), in GFB with FOCE was analyzed. The results showed that the use of FOCE enriched experimental GFB in valuable SDG (217-525 µg/100 g DM) while not causing adverse microbiological changes. A moderate level (25-50%) of FOCE did not change the main texture parameters of GFB stored for 72 h, the quality of which was comparable to control bread without FOCE. Meanwhile, higher proportions of FOCE (75-100% of water replacement) shortened GFB shelf life as determined by water activity and texture profile, suggesting that GFB with FOCE should be consumed fresh. To summarize, FOCE at moderate levels can add value to GFBs without causing a drop in quality, while still fitting in with the idea of zero waste and the circular economy.

Best Practices for Microbial Challenge In-use Studies to Evaluate the Microbial Growth Potential of Parenteral Biological Products; Industry and Regulatory Considerations.

Microbial challenge in-use studies are performed to evaluate the potential for microbial proliferation in preservative-free single dose biological products after first puncture and potential accidental contamination during dose preparation (e.g. reconstitution, dilution) and storage. These studies, in addition to physicochemical in-use stability assessments, are used as part of product registration to define in-use hold times in Prescribing Information and in the pharmacy manual in the case of clinical products. There are no formal guidance documents describing regulator expectations on how to conduct microbial challenge in-use studies and interpret microbial data to assign in-use storage hold-times. In lieu of guidance, US Food and Drug Administration (FDA) regulators have authored publications and presentations describing regulator expectations. Insufficient or unavailable microbial challenge data can result in shortened in-use hold times, thus microbial challenge data enables flexibility for health care providers (HCPs) and patients, while ensuring patient safety. A cross-industry/FDA in-use microbial working group was formed through the Innovation & Quality (IQ) Consortium to gain alignment among industry practice and regulator expectations. The working group assessed regulatory guidance, current industry practice via a blinded survey of IQ Consortium member companies, and scientific rationale to align on recommendations for experimental design, execution of microbial challenge in-use studies, and a decision tree for microbial data interpretation to assign in-use hold times. Besides the study execution and data interpretation, additional considerations are discussed including use of platform data for clinical stage products, closed system transfer devices (CSTDs), transport of dose solutions, long infusion times, and the use of USP <797> by HCPs for preparing sterile drugs for administration. The recommendations provided in this manuscript will help streamline biological product development, ensure consistency on assignment of in-use hold times in biological product labels across industry, and provide maximum allowable flexibility to HCPs and patients, while ensuring patient safety.

Assessment of Chitosan Coating Enriched with Free and Nanoencapsulated Satureja montana L. Essential Oil as a Novel Tool for Beef Preservation.

The effect of chitosan coating enriched with free and nanoencapsulated Satureja montana L. essential oil (EO) on microbial, antioxidant and sensory characteristics of beef was analyzed. Different concentrations of free Satureja montana L. EO (SMEO) and nanoparticles (CNPs) were added to chitosan coatings, namely 0.25%, 0.5% and 1%. The beef samples were immersed in the chitosan coatings and stored at +4 °C for 20 days. In this period, the changes in pH value, total viable count (TVC), lactic acid bacteria, psychrophilic bacteria and Pseudomonas spp. were analyzed. The lipid oxidation of beef was determined by the TBAR assay, while sensory analysis was performed by means of the descriptive evaluation method. Generally, the influence of chitosan coating with CNPs on the growth of the tested microorganisms was more pronounced compared to SMEO. Treatment with coating enriched with 1% CNPs resulted in the reduction in TVC and Pseudomonas spp. by 2.4 and 3 log CFU/g, compared to the control, respectively. Additionally, all applied coatings with SMEO and CNPs resulted in the prolonged oxidative stability of the meat The addition of free SMEO created an unnatural aroma for the evaluators, while this odor was neutralized by nanoencapsulation. The durability of color, smell and general acceptability of beef was significantly increased by application of chitosane coatings with the addition of SMEO or SMEO-CNPs, compared to the control. This research indicates the potential application of enriched chitosan coatings in beef preservation in order to improve meat safety and prolong shelf-life.

Evaluation of Active LDPE Films for Packaging of Fresh Orange Juice.

Microbial development, enzymatic action, and chemical reactions influence the quality of untreated natural orange juice, compromising its organoleptic characteristics and causing nutritional value loss. Active low-density polyethylene (LDPE) films containing green tea extract (GTE) were previously prepared by a blown film extrusion process. Small bags were prepared from the produced films, which were then filled with fresh orange juice and stored at 4 °C. Ascorbic acid (AA) content, sugar content, browning index, color parameters, pH, total acidity (TA) and microbial stability were evaluated after 3, 7, and 14 days of storage. The packaging containing GTE maintained the microbial load of fresh juice beneath the limit of microbial shelf-life (6 log CFU/mL) for the bacterial growth, with a more prominent effect for LDPE with 3%GTE. Regarding yeasts and molds, only the CO_LDPE_3GTE package maintained the microbial load of fresh juice below the limit for up to 14 days. At 14 days, the lowest levels of AA degradation (32.60 mg/100 mL of juice) and development of brown pigments (browning index = 0.139) were observed for the packages containing 3% of GTE, which had a pH of 3.87 and sugar content of 11.4 g/100 mL of juice at this time. Therefore, active LDPE films containing 3% of GTE increase the shelf-life of fresh juice and can be a promising option for storage of this food product while increasing sustainability.

Impact of aqueous ozone mixing on microbiological, quality and physicochemical characteristics of semi-dried buckwheat noodles.

The microbiological, microstructural, and physicochemical impact of aqueous ozone mixing (AOM) on semi-dried buckwheat noodles (SBWN) was elucidated in this study. Microbiological measurements declared that AOM reduced the initial total plate count (TPC) of SBWN significantly (P < 0.05) with a prolonged shelf-life of 2 ~ 5 days. Meanwhile, AOM reduced the cooking loss and water absorption along with the enhancement of hardness and tension force. Scanning electron microscopy (SEM) showed that the protein network of surface and cross section became continuous and compact, and wrapped starch granules more effectively. Moreover, an obvious increase in the intensity of the high molecular protein bands was observed in the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns. Furthermore, the sodium dodecyl sulfate extractable protein (SDSEP) under non-reducing condition obviously decreased, and then the SDSEP under reducing condition changed insignificantly (P > 0.05). These results indicated that AOM mainly promoted the protein cross-linking of SBWN by disulfide bond (SS) cross-links.

Destruction of microbial stability in drinking water distribution systems by trace phosphorus polluted water source.

The effects of trace phosphate concentrations (0, 0.3 and 0.6 mg/L) in water source were investigated on microbial stability of the drinking water distribution systems (DWDSs). Obviously, the results verified that in the effluent of DWDSs simulated by annular reactors (ARs), the total microbial biomass and the absolute concentration of opportunistic pathogens such as Legionella pneumophila, Mycobacterium avium, and Hartmanella vermiformis increased significantly with phosphate concentration increasing. Based on X-ray powder diffractometer and zeta potentials measurement, trace phosphate did change physicochemical properties of corrosion products, hence promoting microbes escape from corrosion products to bulk water to a certain extent. Stimulated by chlorine disinfectant and phosphate, the extracellular polymeric substances (EPS) from the suspended biofilms of AR-0.6 gradually exhibited superior characteristics including higher content, flocculating efficiency, hydrophobicity and tightness degree, contributing to formation of large-scale suspended biofilms with strong chlorine-resistance ability. However, the disinfection by-products concentration in DWDSs barely changed due to the balance of EPS precursors contribution and biodegradation effect, covering up the microbiological water quality risk. Therefore, more attention should be paid to the trace phosphorus polluted water source though its concentration was much lower than wastewater. This is the first study successfully revealing the influence mechanism of trace phosphate on microbial stability in DWDSs, which may help to fully understand the biofilms transformation and microbial community succession in DWDSs.

Fermentation Versus Meat Preservatives to Extend the Shelf Life of Mealworm (Tenebrio molitor) Paste for Feed and Food Applications.

Freshly prepared pastes from blanched mealworms (Tenebrio molitor) are highly perishable and prone to microbial and chemical changes upon storage due to their high water activity, near-neutral pH, and their rich nutrient profile. Their shelf life is short unless preservation methods are used. In this study, the effects of preservatives (sodium nitrite and sodium lactate) and lactic acid fermentation (with the starter cultures Bactoferm® F-LC and Lactobacillus farciminis) on the microbiological and the chemical stability of mealworm pastes stored at 4°C were compared. During the storage experiment, the pH, water activity, color, microbial counts, and fat oxidation were monitored. In addition, the prevalence of the pathogens Bacillus cereus, Salmonella spp., and Listeria monocytogenes were studied. Microbial quality evaluation of the mealworm pastes showed that the addition of preservatives did not inhibit microbial growth during refrigerated storage, reaching the upper limits for consumption between seven and 14 days. By contrast, the acid medium (pH < 4.50) created by fermentation stabilized all microbial populations investigated, indicating that these pastes could be consumed up to (at least) 8 weeks of refrigerated storage. L. monocytogenes, Salmonella, and B. cereus were not detected in any of the samples and lipid oxidation of the samples was minimal. Altogether, this study shows that lactic acid fermentation can be used successfully to inhibit microbial growth, to maintain chemical quality, and to extend the shelf life of mealworm pastes stored at 4°C.