Glutathione metabolism contributes to citric acid tolerance and antioxidant capacity in Acetobacter tropicalis.

Acetobacter is one of the main species producing fruit vinegar and its tolerance mechanism to citric acid has not been fully studied. This limits fruit vinegar production from high-citric-acid fruits, which are excellent materials for fruit vinegar production. This study analyzed the metabolic differences between two strains of A. tropicalis with different citric acid tolerances using non-targeted metabolomics. Differential metabolites and metabolic pathways analysis showed that the enhanced amino acid metabolism significantly improved the citric acid tolerance of A. tropicalis and the deamination of amino acids may also play a role. In addition, the up-regulated phosphatidylcholine (PC) and N-heptanoylhonoserine lactone indicated decreased membrane permeability and enhanced quorum sensing (QS), respectively. The analysis of the interaction between pathways and metabolites indicated that Gln, Cys, and Tyr contribute to improving citric acid tolerance, which was also confirmed by the exogenous addition. After adding the amino acids, the down-regulated qdh, up-regulated ggt, and improved glutathione reductase (GR) activity in J-2736 indicated that glutathione metabolism played an important role in resisting citric acid, and cellular antioxidant capacity was increased. This study provides a theoretical basis for efficient fruit vinegar production from citric-acid-type fruits.

The mechanisms of pH regulation on promoting volatile fatty acids production from kitchen waste.

The anaerobic acid production experiments were conducted with the pretreated kitchen waste under pH adjustment. The results showed that pH 8 was considered to be the most suitable condition for acid production, especially for the formation of acetic acid and propionic acid. The average value of total volatile fatty acid at pH 8 was 8814 mg COD/L, 1.5 times of that under blank condition. The average yield of acetic acid and propionic acid was 3302 mg COD/L and 2891 mg COD/L, respectively. The activities of key functional enzymes such as phosphotransacetylase, acetokinase, oxaloacetate transcarboxylase and succinyl-coA transferase were all enhanced. To further explore the regulatory mechanisms within the system, the distribution of microorganisms at different levels in the fermentation system was obtained by microbial sequencing, results indicating that the relative abundances of Clostridiales, Bacteroidales, Chloroflexi, Clostridium, Bacteroidetes and Propionibacteriales, which were great contributors for the hydrolysis and acidification, increased rapidly at pH 8 compared with the blank group. Besides, the proportion of genes encoding key enzymes was generally increased, which further verified the mechanism of hydrolytic acidification and acetic acid production of organic matter under pH regulation.

Sorlinia euscelidii gen. nov., sp. nov., a novel acetic acid bacterium isolated from the leafhopper Euscelidius variegatus (Hemiptera: Cicadellidae).

Acetic acid bacteria - belonging to the Acetobacteraceae family - are found in the gut of many sugar-feeding insects. In this study, six strains have been isolated from the hemipteran leafhopper Euscelidius variegatus. While they exhibit high 16S rRNA gene sequence similarities to uncultured members of the Acetobacteraceae family, they could not be unequivocally assigned to any particular type species. Considering the clonality of the six isolates, the EV16PT strain was used as a representative of this group of isolates. The genome sequence of EV16PT is composed of a 2.388 Mbp chromosome, with a DNA G+C content of 57 mol%. Phylogenetic analyses based on the 16S rRNA gene sequence and whole-genome multilocus sequence analysis indicate that EV16PT forms a monophyletic clade with the uncultivated endosymbiont of Diaphorina citri, the Candidatus Kirkpatrickella diaphorinae. Such a phylogenetic clade is positioned between those of Asaia-Swaminathania and Kozakia. The genomic distance metrics based on gene and protein sequences support the proposal that EV16PT is a new species belonging to a yet-undescribed genus. It is a rod-shaped Gram-stain-negative bacterium, strictly aerobic, non-motile, non-spore-forming, showing optimal growth without salt (NaCl) at 30 °C and pH of 6-7. The major quinone is Q10, and the dominant cellular fatty acids (>10%) are C18:l ω7c, C19 : 0 cyclo ω6c, C16 : 0 and C19 : 1 2OH. The polar lipid profile comprises diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine, along with unidentified aminophospholipids, glycophospholipids, aminolipids and lipids. Based on a polyphasic approach, including phylogenetic, phylogenomic, genome relatedness, phenotypic and chemotaxonomic characterisations, EV16PT (= KCTC 8296T, = DSM 117028T) is proposed as a representative of a novel species in a novel genus with the proposed name Sorlinia euscelidii gen. nov., sp. nov., in honour of Prof. Claudia Sorlini, an Italian environmental microbiologist at the University of Milan who inspired the research on microbial diversity, including symbiosis in plants and animals.

Responses of microbial community composition and CAZymes encoding gene enrichment in ensiled Elymus nutans to altitudinal gradients in alpine region.

High-throughput metagenomic sequence technology was employed to evaluate changes in microbial community composition and carbohydrate-active enzymes encoding gene enrichment status in Elymus nutans silages to altitudinal gradients in the world's highest alpine region of Qinghai-Tibetan Plateau (QTP). E. nutans were collected from three different altitudes in QTP: 2,600 m (low altitude), 3600 m (moderate altitude), and 4,600 m [high (H) altitude], and ensiled for 7, 14, 30, and 60 d. Results indicated an improvement in silage quality with the increasing altitude, although the acetic acid concentration and dry matter loss were greater in H altitude silages after 30 d of ensiling. Harmful bacteria or potential pathogens predominated in the microbial community on d 7 and 14 of fermentation, while genera belonging to lactic acid bacteria gradually became the main microorganisms with the increasing altitude on d 30 and 60 of ensiling. The abundance of carbohydrate-active enzymes genes responsible for macromolecular carbohydrate degradation in silage increased with increasing altitude, and those genes were mainly carried by Lactiplantibacillus and Pediococcus at 30 and 60 d of ensiling. The abundance of key enzymatic genes associated with glycolysis and organic acid production in carbohydrate metabolism pathway was higher in H altitude silages, and Lactiplantibacillus and Pediococcus were also the main hosts after 30 d of silage fermentation, except for the fact that acetic acid production was also related to genera Leuconostoc, Latilactobacillus, and Levilactobacillus. IMPORTANCE: The fermentation quality of Elymus nutans silage was getting better with the increase of altitude in the Qinghai-Tibetan Plateau. The abundance of hosts carrying carbohydrate-active enzymes genes and key enzyme genes related to organic acid production increased with increasing altitude during the later stages of fermentation. Lactiplantibacillus and Pediococcus were the core microorganisms responsible for both polysaccharide hydrolysis and silage fermentation in the late stage of ensiling. This study provided insights on the influence of different altitudes on the composition and function of silage microbiome in the Qinghai-Tibetan Plateau, and provided a reference approach for improving the quality and controllability of silage production in high altitude areas of the Qinghai-Tibetan Plateau.

Blended nexus molecules promote CO2 to l-tyrosine conversion.

Using CO2 as the primary feedstock offers the potential for high-value utilization of CO2 while forging sustainable pathways for producing valuable natural products, such as l-tyrosine. Cascade catalysis is a promising approach but limited by stringent purity demands of nexus molecules. We developed an abiotic/biotic cascade catalysis using blended nexus molecules for l-tyrosine synthesis. Specifically, we begin by constructing a solid-state reactor to reduce CO2 electrochemically, yielding a mixture of acetic acid and ethanol, which serves as the blended nexus molecules. Subsequently, we use genetic engineering to introduce an ethanol utilization pathway and a tyrosine producing pathway to Escherichia coli to facilitate l-tyrosine production. The ethanol pathway synergistically cooperated with the acetic acid pathway, boosting l-tyrosine production rate (nearly five times higher compared to the strain without ethanol utilization pathway) and enhancing carbon efficiency. Our findings demonstrate that using blended nexus molecules could potentially offer a more favorable strategy for the cascade catalysis aimed at producing valuable natural products.

Genomics and synthetic community experiments uncover the key metabolic roles of acetic acid bacteria in sourdough starter microbiomes.

While research on the sourdough microbiome has primarily focused on lactic acid bacteria (LAB) and yeast, recent studies have found that acetic acid bacteria (AAB) are also common members. However, the ecology, genomic diversity, and functional contributions of AAB in sourdough remain unknown. To address this gap, we sequenced 29 AAB genomes, including three that represent putatively novel species, from a collection of over 500 sourdough starters surveyed globally from community scientists. We found variations in metabolic traits related to carbohydrate utilization, nitrogen metabolism, and alcohol production, as well as in genes related to mobile elements and defense mechanisms. Sourdough AAB genomes did not cluster when compared to AAB isolated from other environments, although a subset of gene functions was enriched in sourdough isolates. The lack of a sourdough-specific genomic cluster may reflect the nomadic lifestyle of AAB. To assess the consequences of AAB on the emergent function of sourdough starter microbiomes, we constructed synthetic starter microbiomes, varying only the AAB strain included. All AAB strains increased the acidification of synthetic sourdough starters relative to yeast and LAB by 18.5% on average. Different strains of AAB had distinct effects on the profile of synthetic starter volatiles. Taken together, our results begin to define the ways in which AAB shape emergent properties of sourdough and suggest that differences in gene content resulting from intraspecies diversification can have community-wide consequences on emergent function. IMPORTANCE: This study is a comprehensive genomic and ecological survey of acetic acid bacteria (AAB) isolated from sourdough starters. By combining comparative genomics with manipulative experiments using synthetic microbiomes, we demonstrate that even strains with >97% average nucleotide identity can shift important microbiome functions, underscoring the importance of species and strain diversity in microbial systems. We also demonstrate the utility of sourdough starters as a model system to understand the consequences of genomic diversity at the strain and species level on multispecies communities. These results are also relevant to industrial and home-bakers as we uncover the importance of AAB in shaping properties of sourdough starters that have direct impacts on sensory notes and the quality of sourdough bread.

Improving the alcohol respiratory chain and energy metabolism by enhancing PQQ synthesis in Acetobacter pasteurianus.

Pyrroloquinoline quinone (PQQ) is one of the important coenzymes in living organisms. In acetic acid bacteria (AAB), it plays a crucial role in the alcohol respiratory chain, as a coenzyme of alcohol dehydrogenase (ADH). In this work, the PQQ biosynthetic genes were overexpressed in Acetobacter pasteurianus CGMCC 3089 to improve the fermentation performance. The result shows that the intracellular and extracellular PQQ contents in the recombinant strain A. pasteurianus (pBBR1-p264-pqq) were 152.53% and 141.08% higher than those of the control A. pasteurianus (pBBR1-p264), respectively. The catalytic activity of ADH and aldehyde dehydrogenase increased by 52.92% and 67.04%, respectively. The results indicated that the energy charge and intracellular ATP were also improved in the recombinant strain. The acetic acid fermentation was carried out using a 5 L self-aspirating fermenter, and the acetic acid production rate of the recombinant strain was 23.20% higher compared with the control. Furthermore, the relationship between the PQQ and acetic acid tolerance of cells was analyzed. The biomass of recombinant strain was 180.2%, 44.3%, and 38.6% higher than those of control under 2%, 3%, and 4% acetic acid stress, respectively. After being treated with 6% acetic acid for 40 min, the survival rate of the recombinant strain was increased by 76.20% compared with the control. Those results demonstrated that overexpression of PQQ biosynthetic genes increased the content of PQQ, therefore improving the acetic acid fermentation and the cell tolerance against acetic acid by improving the alcohol respiratory chain and energy metabolism. ONE SENTENCE SUMMARY: The increase in PQQ content enhances the activity of the alcohol respiratory chain of Acetobacter pasteurianus, and the increase in energy charge enhances the tolerance of cells against acetic acid, therefore, improving the efficiency of acetic acid fermentation.

Hydrogen-producing conditions and mutation mechanisms of a highly efficient mutant strain Ethanoligenens harbinense YR-3.

In this study, the optimal hydrogen (H2) production conditions of the high-efficiency H2-producing mutant strain Ethanoligenens harbinense YR-3 (carbon-nitrogen ratio 5.5, phosphate buffer 80 mM, initial pH 6.0, biotin 1.4 mg/L) are obtained by intermittent experiments. The maximum specific H2 production rate of YR-3 (2.85 mol H2/mol glucose) was 1.4 times that of the wild strain ZGX4 (2.04 mol H2/mol glucose). The liquid-phase products are mainly ethanol and acetic acid, indicating that the metabolic pathway has not changed. Two-dimensional electrophoresis and mass spectrometry were used to compare and analyze the protein map differences between YR-3 and ZGX4. The results show that 1,6-fructose diphosphate aldolase and the flavoprotein in hydrogenase are highly expressed. This study will provide a theoretical basis for the genetic modification of high-efficiency H2-producing strains and the improvement of H2 production capacity.

PTER is a N-acetyltaurine hydrolase that regulates feeding and obesity.

Taurine is a conditionally essential micronutrient and one of the most abundant amino acids in humans1-3. In endogenous taurine metabolism, dedicated enzymes are involved in the biosynthesis of taurine from cysteine and in the downstream metabolism of secondary taurine metabolites4,5. One taurine metabolite is N-acetyltaurine6. Levels of N-acetyltaurine are dynamically regulated by stimuli that alter taurine or acetate flux, including endurance exercise7, dietary taurine supplementation8 and alcohol consumption6,9. So far, the identities of the enzymes involved in N-acetyltaurine metabolism, and the potential functions of N-acetyltaurine itself, have remained unknown. Here we show that the body mass index associated orphan enzyme phosphotriesterase-related (PTER)10 is a physiological N-acetyltaurine hydrolase. In vitro, PTER catalyses the hydrolysis of N-acetyltaurine to taurine and acetate. In mice, PTER is expressed in the kidney, liver and brainstem. Genetic ablation of Pter in mice results in complete loss of tissue N-acetyltaurine hydrolysis activity and a systemic increase in N-acetyltaurine levels. After stimuli that increase taurine levels, Pter knockout mice exhibit reduced food intake, resistance to diet-induced obesity and improved glucose homeostasis. Administration of N-acetyltaurine to obese wild-type mice also reduces food intake and body weight in a GFRAL-dependent manner. These data place PTER into a central enzymatic node of secondary taurine metabolism and uncover a role for PTER and N-acetyltaurine in body weight control and energy balance.

Research advances in technologies and mechanisms to regulate vinegar flavor.

New vinegar needs a long maturing time to improve its poor flavor before sale, which greatly increases its production cost. Therefore, it is urgent to explore regulation technologies to accelerate vinegar flavor maturation. Based on literature and our research, this review introduces the latest advances in flavor regulation technologies of vinegar including microbial fortification/multi starters fermentation, key production processes optimization and novel physical processing technologies. Microbial fortification or multi starters fermentation accelerates vinegar flavor maturation via enhancing total acids, esters and aroma precursors content in vinegar. Adjusting raw materials composition, fermentation temperature, and oxygen flow reasonably increase alcohols, organic acids, polyphenols and esters levels via generating more corresponding precursors in vinegar, thereby improving its flavor. Furthermore, novel processing technologies greatly promote conversion of alcohols into acids and esters in vinegar, shortening flavor maturation time for over six months. Meanwhile, the corresponding mechanisms are discussed and future research directions are addressed.

Characterization of cellulose produced by bacteria isolated from different vinegars.

Traditional vinegars are naturally produced from sugar- or starch-containing raw materials, through alcoholic fermentation followed by acetic fermentation. Fermentation is a spontaneous and complex process involving interactions between various microorganisms. In this study, we produced vinegar using traditional methods from six fruits: rosehip, pear, fig, wild pear, apple, and plum. Bacteria that produce bacterial cellulose (BC) were isolated from these vinegars and identified. In addition, we investigated the properties of BC produced from these bacteria. The strains isolated from vinegars were identified as Gluconobacter oxydans strain MG2022, Acetobacter tropicalis strain MG2022, Acetobacter fabarum strain MG2022, Komagataeibacter saccharivorans strain MG2022, K. saccharivorans strain EG2022, and Acetobacter lovaniensis strain OD2022. In total, 0.83-2.04 g/L BC was produced and the bacterial strain isolated from pear vinegar yielded the most BC. BC produced by the bacterial strain isolated from wild pear vinegar had the highest thermal stability and crystallinity (87.44 %). Overall, this study shows that different fruits contain different BC-producing bacteria in their natural flora and vinegars obtained from fruits can be used in BC production. Also, different BC-producing bacteria can be isolated from different vinegars, and BC produced by these bacteria might have different properties.

Acetic and citric acids effect the type II secretion system and decrease the metabolic activities of salmon spoilage-related Rahnella aquatilis KM05.

Rahnella aquatilis causes seafoods to spoil by metabolizing sulfur-containing amino acids and/or proteins, producing H2S in products. The type II secretion system (T2SS) regulates the transport of proteases from the cytoplasm to the surrounding environment and promotes bacterial growth at low temperatures. To prevent premature fish spoilage, new solutions for inhibiting the T2SS of bacteria should be researched. In this study, global transcriptome sequencing was used to analyze the spoilage properties of R. aquatilis KM05. Two of the mapped genes/coding sequences (CDSs) were matched to the T2SS, namely, qspF and gspE, and four of the genes/CDSs, namely, ftsH, rseP, ptrA and pepN, were matched to metalloproteases or peptidases in R. aquatilis KM05. Subinhibitory concentrations of citric (18 µM) and acetic (41 µM) acids caused downregulation of T2SS-related genes (range from - 1.0 to -4.5) and genes involved in the proteolytic activities of bacteria (range from - 0.5 to -4.0). The proteolytic activities of R. aquatilis KM05 in vitro were reduced by an average of 40%. The in situ experiments showed the antimicrobial properties of citric and acetic acids against R. aquatilis KM05; the addition of an acidulant to salmon fillets limited microbial growth. Citric and acetic acids extend the shelf life of fish-based products and prevent food waste.

Exploring volatile compounds and microbial dynamics: Kluyveromyces marxianus and Hanseniaspora opuntiae reduce Forastero cocoa fermentation time.

Traditional cocoa bean fermentation is a spontaneous process and can result in heterogeneous sensory quality. For this reason, yeast-integrated starter cultures may be an option for creating consistent organoleptic profiles. This study proposes the mixture of Hanseniaspora opuntiae and Kluyveromyces marxianus (from non-cocoa fermentation) as starter culture candidates. The microorganisms and volatile compounds were analyzed during the cocoa fermentation process, and the most abundant were correlated with predominant microorganisms. Results showed that Kluyveromyces marxianus, isolated from mezcal fermentation, was identified as the dominant yeast by high-throughput DNA sequencing. A total of 63 volatile compounds identified by HS-SPME-GC-MS were correlated with the more abundant bacteria and yeast using Principal Component Analysis and Agglomerative Hierarchical Clustering. This study demonstrates that yeasts from other fermentative processes can be used as starter cultures in cocoa fermentation and lead to the formation of more aromatic esters, decrease the acetic acid content.

Activation of the yeast Retrograde Response pathway by adaptive laboratory evolution with S-(2-aminoethyl)-L-cysteine reduces ethanol and increases glycerol during winemaking.

BACKGROUND: Global warming causes an increase in the levels of sugars in grapes and hence in ethanol after wine fermentation. Therefore, alcohol reduction is a major target in modern oenology. Deletion of the MKS1 gene, a negative regulator of the Retrograde Response pathway, in Saccharomyces cerevisiae was reported to increase glycerol and reduce ethanol and acetic acid in wine. This study aimed to obtain mutants with a phenotype similar to that of the MKS1 deletion strain by subjecting commercial S. cerevisiae wine strains to an adaptive laboratory evolution (ALE) experiment with the lysine toxic analogue S-(2-aminoethyl)-L-cysteine (AEC). RESULTS: In laboratory-scale wine fermentation, isolated AEC-resistant mutants overproduced glycerol and reduced acetic acid. In some cases, ethanol was also reduced. Whole-genome sequencing revealed point mutations in the Retrograde Response activator Rtg2 and in the homocitrate synthases Lys20 and Lys21. However, only mutations in Rtg2 were responsible for the overactivation of the Retrograde Response pathway and ethanol reduction during vinification. Finally, wine fermentation was scaled up in an experimental cellar for one evolved mutant to confirm laboratory-scale results, and any potential negative sensory impact was ruled out. CONCLUSIONS: Overall, we have shown that hyperactivation of the Retrograde Response pathway by ALE with AEC is a valid approach for generating ready-to-use mutants with a desirable phenotype in winemaking.

Differential impacts of furfural and acetic acid on the bioenergetics and fermentation performance of Scheffersomyces stipitis.

Lignocellulosic material is a leading carbon source for economically viable biotechnological processes; however, compounds such furfural and acetic acid exhibit toxicity to yeasts. Nonetheless, research about the molecular mechanism of furfural and acetic acid toxicity is still scarce in yeasts like Scheffersomyces stipitis. Thus, this study aims to elucidate the impact of furfural and acetic acid on S. stipitis regarding bioenergetic and fermentation parameters. Here, we provide evidence that furfural and acetic acid induce a delay in cell growth and extend the lag phase. The mitochondrial membrane potential decreased in all treatments with no significant differences between inhibitors or concentrations. Interestingly, reactive oxygen species increased when the inhibitor concentrations were from 0.1 to 0.3 % (v/v). The glycolytic flux was not significantly (p > 0.05) altered by acetic acid, but furfural caused different effects. Ethanol production decreased significantly (4.32 g·L-1 in furfural and 5.06 g·L-1 in acetic acid) compared to the control (26.3 g·L-1). In contrast, biomass levels were not significantly different in most treatments compared to the control. This study enhances our understanding of the effects of furfural and acetic acid at the mitochondrial level in a pentose-fermenting yeast like S. stipitis.

The ldh Gene Plays a Crucial Role in Mediating the Pathogen Control of Lactiplantibacillus plantarum AR113.

Effectively managing foodborne pathogens is imperative in food processing, where probiotics play a crucial role in pathogen control. This study focuses on the Lactiplantibacillus plantarum AR113 and its gene knockout strains, exploring their antimicrobial properties against Escherichia coli O157:H7 and Staphylococcus aureus. Antimicrobial assays revealed that the inhibitory effect of AR113 increases with its growth and the potential bacteriostatic substance is acidic. AR113Δldh, surpassed AR113Δ0273&2024, exhibited a complete absence of bacteriostatic properties, which indicates that lactic acid is more essential than acetic acid in the bacteriostatic effect of AR113. However, the exogenous acid validation test affirmed the equivalent superior bacteriostatic effect of lactic acid and acetic acid. Notably, AR113 has high lactate production and deletion of the ldh gene not only lacks lactate production but also affects acetic production. This underscores the ldh gene's pivotal role in the antimicrobial activity of AR113. In addition, among all the selected knockout strains, AR113ΔtagO and ΔccpA also had lower antimicrobial effects, suggesting the importance of tagO and ccpA genes of AR113 in pathogen control. This study contributes insights into the antimicrobial potential of AR113 and stands as the pioneering effort to use knockout strains for comprehensive bacteriostatic investigations.

Development of an Haa1-Based Biosensor for Acetic Acid Sensing in Saccharomyces cerevisiae.

Transcription factor (TF)-based biosensors are important tools in strain development and screening as they can allow accurate monitoring of intracellular concentrations of a molecule. Acetic acid is one of the main inhibitors in lignocellulosic biomass and a major challenge when using yeast cell factories for biorefinery applications. Thus, developing acetic acid tolerant strains is of great importance. The acetic acid sensing biosensor developed relies on the endogenous Saccharomyces cerevisiae TF Haa1 that upon binding of acetic acid translocates to the nucleus. The acetic acid biosensor can be used as a tool for strain development and evaluation, as well as for screening of acetic acid-producing strains and for dynamic monitoring of acetic acid accumulation. This chapter describes a methodology for developing a TF-based biosensor for acetic acid sensing. Protocols for design considerations, part construction, and characterization procedures are included. The approach can potentially be adapted to any molecule where a suitable TF can be identified.

Bamboo vinegar regulates the phytoremediation efficiency of Perilla frutescens (L.) Britt. by reducing membrane lipid damage and increasing cadmium retention.

The gap between serious soil heavy metals pollution and inefficient soil remediation threatens human health. This study proposed a method to improve the phytoremediation efficiency using bamboo vinegar (BV) solution and the potential mechanism was discussed. The results demonstrated that the application of BV increases the content of cadmium (Cd) in vacuole and cell wall hemicellulose 2 in leaves of Perilla frutescens. Simultaneously, it enhanced enzyme activities of superoxide dismutase and catalase in leaves. Therefore, this process alleviated the damage of Cd to functional tissues of Perilla frutescens, thus improving the tolerance of plants to Cd. Moreover, the BV application reduced the Cd content bound by root cell wall pectin fractions and insoluble phosphate, subsequently improving the ability of oxalic acids to carry Cd to the aerial parts. Consequently, the aerial parts obtained a larger amount of Cd enrichment. Overall, the Transfer Factor of Cd from roots to stems and enrichment of Cd in Perilla frutescens were maximally increased by 57.70 % and 54.03 % with the application of 50-fold and 300-fold diluted BV under 2 mg·L-1 Cd stress, respectively. The results can provide a theoretical basis for the promotion of phytoremediation of Cd-contaminated soil treatment technology.

Ionic liquid coupled plasma promotes acetic acid production during anaerobic fermentation of waste activated sludge: Breaking the restrictions of low bioavailable substrates and altering the metabolic activities of anaerobes.

This study explored the potential application of plasma coupling ionic liquid on disintegration of waste activated sludge and enhanced production of short-chain fatty acids (SCFAs) in anaerobic fermentation. Under optimal conditions (dosage of ionic liquid [Emim]OTf = 0.1 g/g VSS (volatile suspended solids) and discharge power of dielectric barrier discharge plasma (DBD) = 75.2 W), the [Emim]OTf/DBD pretreatment increased SCFA production by 302 % and acetic acid ratio by 53 % compared to the control. Mechanistic investigations revealed that the [Emim]OTf/DBD combination motivated the generation of various reactive species (such as H2O2, O3, •OH, 1O2, ONOO-, and •O2-) and enhanced the utilization of physical energies (such as heat). The coupling effects of [Emim]OTf/DBD synergistically improved the disintegration of sludge and biodegradability of dissolved organic matter, promoting the sludge anaerobic fermentation process. Moreover, the [Emim]OTf/DBD pretreatment enriched hydrolysis and SCFAs-forming bacteria while inhibiting SCFAs-consuming bacteria. The net effect was pronounced expression of genes encoding key enzymes (such as alpha-glucosidase, endoglucanase, beta-glucosidase, l-lactate/D-lactate dehydrogenase, and butyrate kinase) involved in the SCFA-producing pathway, enhancing the production of SCFAs from sludge anaerobic fermentation. In addition, [Emim]OTf/DBD pretreatment facilitated sludge dewatering and heavy metal removal. Therefore, [Emim]OTf/DBD pretreatment is a promising approach to advancing sludge reduction, recyclability, and valuable resource recovery.

Enhancing small-scale acetification processes using adsorbed Acetobacter pasteurianus UMCC 2951 on κ-carrageenan-coated luffa sponge.

Background: This study explored the utilization of luffa sponge (LS) in enhancing acetification processes. LS is known for having high porosity and specific surface area, and can provide a novel means of supporting the growth of acetic acid bacteria (AAB) to improve biomass yield and acetification rate, and thereby promote more efficient and sustainable vinegar production. Moreover, the promising potential of LS and luffa sponge coated with κ-carrageenan (LSK) means they may represent effective alternatives for the co-production of industrially valuable bioproducts, for example bacterial cellulose (BC) and acetic acid. Methods: LS and LSK were employed as adsorbents for Acetobacter pasteurianus UMCC 2951 in a submerged semi-continuous acetification process. Experiments were conducted under reciprocal shaking at 1 Hz and a temperature of 32 °C. The performance of the two systems (LS-AAB and LSK-AAB respectively) was evaluated based on cell dry weight (CDW), acetification rate, and BC biofilm formation. Results: The use of LS significantly increased the biomass yield during acetification, achieving a CDW of 3.34 mg/L versus the 0.91 mg/L obtained with planktonic cells. Coating LS with κ-carrageenan further enhanced yield, with a CDW of 4.45 mg/L. Acetification rates were also higher in the LSK-AAB system, reaching 3.33 ± 0.05 g/L d as opposed to 2.45 ± 0.05 g/L d for LS-AAB and 1.13 ± 0.05 g/L d for planktonic cells. Additionally, BC biofilm formation during the second operational cycle was more pronounced in the LSK-AAB system (37.0 ± 3.0 mg/L, as opposed to 25.0 ± 2.0 mg/L in LS-AAB). Conclusions: This study demonstrates that LS significantly improves the efficiency of the acetification process, particularly when enhanced with κ-carrageenan. The increased biomass yield, accelerated acetification, and enhanced BC biofilm formation highlight the potential of the LS-AAB system, and especially the LSK-AAB variant, in sustainable and effective vinegar production. These systems offer a promising approach for small-scale, semi-continuous acetification processes that aligns with eco-friendly practices and caters to specialized market needs. Finally, this innovative method facilitates the dual production of acetic acid and bacterial cellulose, with potential applications in biotechnological fields.