Aggregation-Induced Emission (AIE) in Polymers: Effect of Polymer size on the Fluorescence of Low Molecular Weight PEG and PPG.

Aggregation-induced emission (AIE) is a fascinating phenomenon where specific molecules exhibit enhanced fluorescence upon aggregation. This unique property has revolutionized the design and development of new fluorescent materials for different applications, from biosensors and organic light-emitting diodes (OLEDs) to biomedical imaging and diagnostics. Researchers are creating sensitive and selective sensing platforms, opening new avenues in material science and engineering by harnessing the potential of AIE. To expand the knowledge in this field, this study explored the aggregation-induced emission (AIE) properties of two polymers, namely polyethylene glycol (PEG) and polypropylene glycol (PPG) of low molecular weight (MW) using fluorescence spectroscopy and absorbance (UV). PEG-300 and PPG-725 were the most fluorescent polymers at UV of the ten investigated. Interestingly, AIE did not correlate linearly with molecular weight (MW), and monobutyl ether substitution in PEG with a similar MW substantially altered its AIE. Furthermore, fluorescence precisely quantified low polymer concentrations in water, and non-aqueous solvents suppressed AIE, suggesting potential for AIE manipulation. These findings enhance our understanding of AIE in polymers, fostering the development of novel materials for applications such as biosensors.

Symbiotic microparticles produced through spray-drying-induced in situ alginate crosslinking for the preservation of Pediococcus pentosaceus viability.

Probiotic microorganisms are a promising alternative to antibiotics in preventing and treating bacterial infections. Within the probiotic group, the lactic acid bacteria (LAB)stand out for their health benefits and for being recognized as safe by regulatory agencies. However, these microorganisms are sensitive to various environmental conditions, including the acidic environment of the stomach. Faced with these obstacles, this work aimed to promote the symbiotic microencapsulation of LAB in a composite matrix of alginate and prebiotics to enhance their survival and improve their probiotic activity during gastrointestinal transit. We evaluated the effect of inulin, fructo-oligosaccharides (FOS) and mannan-oligosaccharides (MOS) as prebiotic sources on the growth of Pediococcus pentosaceus LBM34 strain, finding that MOS favored LAB growth and maintenance of microencapsulated cell viability. The symbiotic microparticles were produced using the spray-drying technique with an average size of 10 µm, a smooth surface, and a composition that favored the stabilization of live cells according to the FTIR and the thermal analysis of the material. The best formulation was composed of 1 % of alginate, 10 % MOS and 1 % M10 (% w/v), which presented notable increases in the survival rates of the probiotic strain in both alkaline and acidic conditions. Therefore, this industrially scalable approach to symbiotic LAB microencapsulation can facilitate their growth and colonization within the host. This effort aims to contribute to reducing antibiotic reliance and mitigating the emergence of new zoonotic diseases, which pose significant challenges to public health.

Enhanced production of N-acetyl-glucosaminidase by marine Aeromonas caviae CHZ306 in bioreactor.

N-Acetyl-glucosaminidases (GlcNAcases) are exoenzymes found in a wide range of living organisms, which have gained great attention in the treatment of disorders related to diabetes, Alzheimer's, Tay-Sachs', and Sandhoff's diseases; the control of phytopathogens; and the synthesis of bioactive GlcNAc-containing products. Aiming at future industrial applications, in this study, GlcNAcase production by marine Aeromonas caviae CHZ306 was enhanced first in shake flasks in terms of medium composition and then in bench-scale stirred-tank bioreactor in terms of physicochemical conditions. Stoichiometric balance between the bioavailability of carbon and nitrogen in the formulated culture medium, as well as the use of additional carbon and nitrogen sources, played a central role in improving the bioprocess, considerably increasing the enzyme productivity. The optimal cultivation medium was composed of colloidal α-chitin, corn steep liquor, peptone A, and mineral salts, in a 5.2 C:N ratio. Optimization of pH, temperature, colloidal α-chitin concentration, and kLa conditions further increased GlcNAcase productivity. Under optimized conditions in bioreactor (i.e., 34 °C, pH 8 and kLa 55.2 h-1), GlcNAcase activity achieved 173.4 U.L-1 after 12 h of cultivation, and productivity no less than 14.45 U.L-1.h-1 corresponding to a 370-fold enhancement compared to basal conditions.

Deconstructing sugarcane bagasse lignocellulose by acid-based deep eutectic solvents to enhance enzymatic digestibility.

Biorefinery with deep eutectic solvent (DES) is an emerging processing technology to overcome the shortcomings of conventional biomass pretreatments. This work evaluates the biorefinery of sugarcane bagasse (SCB) with DES formulated with choline chloride as hydrogen bond acceptor and three hydrogen bond donors: lactic acid, citric acid, and acetic acid. Acetic acid showed unique ionic properties responsible for the selective removal of lignin and the deconstruction of cellulose to improve the digestibility of up to 97.61 % of glucan and 63.95 % of xylan during enzymatic hydrolysis. In addition, the structural characteristics of the polysaccharide-rich material (PRM) were analyzed by X-rays, ATR-FTIR, SEM, and enzymatic hydrolysis, and compared with the original material sample, for a comprehensive understanding of biomass deconstruction using different hydrogen bond donors (HBD) as DES pretreatment.

Whole cells of recombinant CYP153A6-E. coli as biocatalyst for regioselective hydroxylation of monoterpenes.

Optimized recombinant whole cells of E. coli bearing CYP153A6 were employed for catalyzing the hydroxylation of different monoterpene derivatives. In most cases, high selectivity was observed with exclusive hydroxylation of the allylic methyl group bound to the aliphatic ring. In the case of (R)- and (S)-carvone, hydroxylation occurred also on the other allylic methyl group, although to a lesser extent. Biotransformations carried out in fed-batch mode on (S)-limonene and α-terpineol showed that recombinant whole cells retained activity for at least 24 h, allowing for the recovery of 3.25 mg mL-1 of (S)-perillyl alcohol and 5.45 mg mL-1 of 7-hydroxy-α-terpineol, respectively.

Bacteriocin-like inhibitory substances production by Enterococcus faecium 135 in co-culture with Ligilactobacillus salivarius and Limosilactobacillus reuteri.

The use of lactic acid bacteria (LAB) and probiotic cultures in the breeding of animals such as poultry and swine are quite common. It is known that those strains can produce bacteriocins when grown in pure culture. However, the production of bacteriocin using co-culture of microorganisms has not been much studied so far. The present study contributes with innovation in this area by embracing the production of bacteriocin-like inhibitory substances (BLIS) by a newly isolated strain of Enterococcus faecium 135. Additionally, the co-cultivation of this strain with Ligilactobacillus salivarius and Limosilactobacillus reuteri was also investigated. The antimicrobial activity of the produced BLIS was evaluated against Listeria monocytogenes, Listeria innocua, Salmonella enterica, and Salmonella enterica serovar Typhimurium using two methods: turbidimetric and agar diffusion. In addition, the presence of enterocin genes was also evaluated. The BLIS produced showed a bacteriostatic effect against the bio-indicator strains, and the highest antimicrobial activities expressed by arbitrary units per mL (AU/mL) were obtained against L. monocytogenes in monoculture (12,800 AU/mL), followed by the co-culture of E. faecium with Limosilactobacillus reuteri (400 AU/mL). After concentration with ammonium sulfate, the antimicrobial activity raised to 25,600 AU/mL. Assays to determine the proteinaceous nature of the BLIS showed susceptibility to trypsin and antimicrobial activity until 90 °C. Finally, analysis of the presence of structural genes of enterocins revealed that four enterocin genes were present in E. faecium 135. These results suggest that BLIS produced by E. faecium 135 has potential to be a bacteriocin and, after purification, could potentially be used as an antimicrobial agent in animal breeding.

Soymilk fermentation: effect of cooling protocol on cell viability during storage and in vitro gastrointestinal stress.

This work covers soymilk fermentation by starter and probiotic cultures and explores the influence of cooling protocol on cell viability, organic acid production, sugar consumption, fatty acid profile, and cell survival to in vitro gastrointestinal stress. After fermentation at 37 °C by mono- or co-cultures of Streptococcus thermophilus (St), Lactobacillus bulgaricus (Lb), and Lactobacillus paracasei (Lp), fermented soymilk was cooled directly at 4 °C for 28 days or cooled in two phases (TPC), i.e., by preceding that step by another at 25 °C for 8 h. Soybean milk fermentation by Lb alone lasted longer (15 h) than by StLb or StLbLp (9 h). In ternary culture, TPC increased Lp viability, linoleic, and lactic acid concentrations by 3.8, 22.6, and 96.2%, respectively, whereas the cooling protocol did not influence Lp and St counts after in vitro gastrointestinal stress. Graphical abstract.

Antibacterial and antifungal activity of crude and freeze-dried bacteriocin-like inhibitory substance produced by Pediococcus pentosaceus.

Pediococcus pentosaceus LBM 18 has shown potential as producer of an antibacterial and antifungal bacteriocin-like inhibitory substance (BLIS). BLIS inhibited the growth of spoilage bacteria belonging to Lactobacillus, Enterococcus and Listeria genera with higher activity than Nisaplin used as control. It gave rise to inhibition halos with diameters from 9.70 to 20.00 mm, with Lactobacillus sakei being the most sensitive strain (13.50-20.00 mm). It also effectively suppressed the growth of fungi isolated from corn grain silage for up to 25 days and impaired morphology of colonies by likely affecting fungal membranes. These results point out that P. pentosaceus BLIS may be used as a new promising alternative to conventional antibacterial and antifungal substances, with potential applications in agriculture and food industry as a natural bio-controlling agent. Moreover, cytotoxicity and cell death induction tests demonstrated cytotoxicity and toxicity of BLIS to human colon adenocarcinoma Caco-2cells but not to peripheral blood mononuclear cells, with suggests possible applications of BLIS also in medical-pharmaceutical applications.

Buffalo milk increases viability and resistance of probiotic bacteria in dairy beverages under in vitro simulated gastrointestinal conditions.

Probiotic dairy beverages prepared from buffalo and cow milks with different levels of whey (0, 25, and 50%) were evaluated for kinetic fermentation parameters, protein and fat contents, post-acidification profile, viability of Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus acidophilus during 21 d of refrigerated storage, and resistance to in vitro gastrointestinal conditions. Progressive acidification that occurred during storage of all dairy products was reduced in the presence of whey. Lactic acid bacteria showed viable cell counts at the end of shelf life, with the highest values (7.33 to 8.83 log cfu/mL) detected in buffalo dairy products. Compared with fermented cow milk products, those made with buffalo milk showed better bacterial viability during in vitro simulated gastrointestinal digestion, which suggests a beneficial protective effect on human microbiome.

Cheese whey permeate fermentation by Kluyveromyces lactis: a combined approach to wastewater treatment and bioethanol production.

Cheese whey is a dairy industry by-product responsible for serious environmental problems. Its fermentation would allow reducing its environmental impact and producing, at the same time, high-value products, hence ensuring cleaner production. Batch fermentations of cheese whey permeate, either as such or 1.5-fold or twice-concentrated, by Kluyveromyces lactis CBS2359 were performed in flasks with or without agitation to select the best conditions to produce simultaneously ethanol and biomass with high ß-galactosidase activity. In shake cultures, the highest ethanol concentration (15.0 g L-1), yield on consumed lactose (0.47 g g-1) and productivity (0.31 g L-1 h-1), were obtained on cheese whey permeate as such, corresponding to 87.4% fermentation efficiency, but ß-galactosidase activity was disappointing (449.3-680.0 U g-1). In static cultures on twice-concentrated whey permeate, despite a decrease in fermentation efficiency and yield, ethanol production increased by 48% and ß-galactosidase activity by no less than 209-367%. Therefore, cheese whey should be considered an alternative feedstock rather than an undesirable dairy industry by-product.

Effects of pH and sugar supplements on bacteriocin-like inhibitory substance production by Pediococcus pentosaceus.

To improve bacteriocin-like inhibitory substance (BLIS) production by Pediococcus pentosaceus ATCC 43200, the influence of pH as well as the addition of sugars-either prebiotic (inulin) or not (sucrose)-on its metabolism were investigated. This strain was grown at pH 5.0 or 6.0 either in glucose-based MRS medium (control) or after addition of 0.5, 1.0 or 1.5% (w/w) sucrose and inulin (GSI-MRS) in the same percentages. In the control medium at pH 5.0, cell mass concentration after 48 h of fermentation (Xmax = 2.26 g/L), maximum specific growth rate (µmax = 0.180 h-1) and generation time (Tg = 3.84 h) were statistically coincident with those obtained in supplemented media. At pH 6.0 some variations occurred in these parameters between the control medium (Xmax = 2.68 g/L; µmax = 0.32 h-1; Tg = 2.17 h) and the above supplemented media (Xmax = 1.90, 2.52 and 1.86 g/L; µmax = 0.26, 0.33 and 0.32 h-1; Tg = 2.62, 2.06 and 2.11 h, respectively). Lactate production was remarkable at both pH values (13 and 16 g/L) and improved in all supplemented media, being 34 and 54% higher than in their respective control media, regardless of the concentration of these ingredients. Cell-free supernatant of the fermented control medium at pH 5.0 displayed an antimicrobial activity against Enterococcus 101 5.3% higher than that at pH 6.0 and even 20% higher than those of all supplemented media, regardless of the concentration of supplements. BLIS production was favored either at pH 5.0 or in the absence of any additional supplements, which were able, instead, to stimulate growth and lactate production by P. pentosaceus.

Application of nisin as biopreservative of pork meat by dipping and spraying methods.

Comparison between dipping and spraying methods to inhibit bacterial growth on artificially contaminated pork meat showed greater effectiveness of the latter method during the whole low-temperature one-week storage of product. These results suggest that the spraying method could be successful in directly applying antimicrobials to food products.

Inhibitory substances production by Lactobacillus plantarum ST16Pa cultured in hydrolyzed cheese whey supplemented with soybean flour and their antimicrobial efficiency as biopreservatives on fresh chicken meat.

Cheese whey, the main byproduct of the dairy industry, is one of the most worrisome types of industrial waste, not only because of its abundant annual global production but also because it is a notable source of environmental pollution. However, cheese whey can serve as a raw material for the production of biocomposites. In this context, in this study, we assayed the production of a bacteriocin-like inhibitory substance (BLIS) and lactate by culturing Lactobacillus plantarum ST16Pa in hydrolyzed fresh cheese whey. The process was improved by studying the enzymatic hydrolysis of cheese whey as well as its supplementation with soybean flour under microaerophilic or anaerobic conditions. Thus, the highest values of BLIS (7367.23 arbitrary units [AU]/mL) and lactate yield (Ylactate/lactose=1.39g/g) were achieved after addition of 10g/L soybean flour in microaerophilia. These conditions were successfully scaled up in a bioreactor because during complete anaerobiosis at 150rpm, L. plantarum ST16Pa attained considerable cell growth (3.14g/L), lactate concentration (14.33g/L), and BLIS activity (8082.56AU/mL). In addition, the cell-free supernatant resulting from this bioprocess showed high biopreservative efficiency in chicken breast fillets artificially contaminated with Enterococcus faecium 711 during 7days of refrigerated storage, thus indicating the potential use of this BLIS as a biopreservative in the food industry.

Stimulating Effects of Sucrose and Inulin on Growth, Lactate, and Bacteriocin Productions by Pediococcus pentosaceus.

Sucrose and inulin, when combined with glucose, behaved as stimulating agents of bacteriocin production by Pediococcus pentosaceus ATCC 43200. When such microbial strain was grown in glucose-based Man, Rogosa, and Sharpe (MRS) medium, without any additional supplement, it showed higher maximum cell concentration (2.68 ± 1.10 g/L) and longer generation time (2.17 ± 0.02 h), but lower specific growth rate (0.32 ± 0.01 h-1) than in the same medium supplemented with 1.0% of both ingredients (2.53 ± 1.10 g/L, 1.60 ± 0.05 h and 0.43 ± 0.02 h-1, respectively). Glucose replacement by sucrose or inulin almost completely suppressed growth, hence confirming that it is the preferred carbon source for this strain. Qualitatively, similar results were observed for lactate production, which was 59.8% higher in glucose-based medium. Enterococcus and Listeria strains were sensitive to bacteriocin, whose antimicrobial effect after 8 h increased from 120.25 ± 0.35 to 144.00 ± 1.41 or 171.00 ± 1.41 AU/mL when sucrose or inulin was added to the glucose-based MRS medium. Sucrose and inulin were also able to speed up P. pentosaceus growth in the exponential phase.

Development of a high-yielding bioprocess for 11-α hydroxylation of canrenone under conditions of oxygen-enriched air supply.

A high yielding bioprocess for 11-α hydroxylation of canrenone (1a) using Aspergillus ochraceus ATCC 18500 was developed. The optimization of the biotransformation involved both fermentation (for achieving highly active mycelium of A. ochraceus) and biotransformation with the aim to obtain 11-α hydroxylation with high selectivity and yield. A medium based on sucrose as C-source resulted particularly suitable for conversion of canrenone into the corresponding 11-hydroxy derivative, whereas the use of O2-enriched air and dimethyl sulfoxide (DMSO) as a co-solvent for increasing substrate solubility played a crucial role for obtaining high yields (>95%) of the desired product in high chemical purity starting from 30mM (10.2g/L) of substrate. The structure of the hydroxylated product was confirmed by a combination of two-dimensional NMR proton-proton correlation techniques.

Optimisation of cheese whey enzymatic hydrolysis and further continuous production of antimicrobial extracts by Lactobacillus plantarum CECT-221.

The enzymatic hydrolysis of cheese whey was optimised using the enzymes iZyme, Alcalase or Flavourzyme under different conditions. Hydrolysates supplemented with commercial nutrients were evaluated as fermentation broths to produce DL-3-Phenyllactic acid (PLA) from phenylalanine (Phe) by Lactobacillus plantarum CECT-221. Optimised hydrolysates were obtained using Flavourzyme at 50 °C and 100 rpm during 12 h, and assayed in 250 ml Erlenemyer flasks using different proportions of vinasses as economic nutrient. The process was then scaled up using a 2 litres Bioreactor working under the continuous modality. Under the intermediate dilution rate of 0·0207 h-1 0·81 ± 0·026 mM of PLA and 38·8 ± 3·253 g/l of lactic acid were produced. A final evaluation revealed that lactic acid, and bacteriocins exerted the highest inhibitory effect among the extracted components of cell-free supernatants.

Use of Vine-Trimming Wastes as Carrier for Amycolatopsis sp. to Produce Vanillin, Vanillyl Alcohol, and Vanillic Acid.

Raw vine-trimming wastes or the solid residues obtained after different fractionation treatments were evaluated for their suitability as Amycolatopsis sp. immobilization carriers during the bioconversion of ferulic acid into valuable phenolic compounds such as vanillin, vanillyl alcohol, and vanillic acid, the main flavor components of vanilla pods. Previously, physical-chemical characteristics of the materials were determined by quantitative acid hydrolysis and water absorption index (WAI), and microbiological characteristics by calculating the cell retention in the carrier (λ). Additionally, micrographics of carrier surface were obtained by field emission-scanning electron microscopy to study the influence of morphological changes during pretreatments in the adhesion of cells immobilized. The results point out that in spite of showing the lowest WAI and intermediate λ, raw material was the most appropriated substrate to conduct the bioconversion, achieving up to 262.9 mg/L phenolic compounds after 24 h, corresponding to 42.9 mg/L vanillin, 115.6 mg/L vanillyl alcohol, and 104.4 mg/L vanillic acid. The results showed the potential of this process to be applied for biotechnological production of vanillin from ferulic acid solutions; however, further studies must be carried out to increase vanillin yield. Additionally, the liquors obtained after treatment of vine-trimming wastes could be assayed to replace synthetic ferulic acid.

Study of the potential of the air lift bioreactor for xylitol production in fed-batch cultures by Debaryomyces hansenii immobilized in alginate beads.

Cell immobilization has shown to be especially adequate for xylitol production. This work studies the suitability of the air lift bioreactor for xylitol production by Debaryomyces hansenii immobilized in Ca-alginate operating in fed-batch cultures to avoid substrate inhibition. The results showed that the air lift bioreactor is an adequate system since the minimum air flow required for fluidization was even lower than that leading to the microaerobic conditions that trigger xylitol accumulation by this yeast, also maintaining the integrity of the alginate beads and the viability of the immobilized cells until 3 months of reuses. Maximum productivities and yields of 0.43 g/l/h and 0.71 g/g were achieved with a xylose concentration of 60 g/l after each feeding. The xylose feeding rate, the air flow, and the biomass concentration at the beginning of the fed-batch operation have shown to be critical parameters for achieving high productivities and yields. Although a maximum xylitol production of 139 g/l was obtained, product inhibition was evidenced in batch experiments, which allowed estimating at 200 and 275 g/l the IC50 for xylitol productivity and yield, respectively. The remarkable production of glycerol in the absence of glucose was noticeable, which could not only be attributed to the osmoregulatory function of this polyol in conditions of high osmotic pressure caused by high xylitol concentrations but also to the role of the glycerol synthesis pathway in the regeneration of NAD(+) in conditions of suboptimal microaeration caused by insufficient aeration or high oxygen demand when high biomass concentrations were achieved.

Bacteriocin production by Bifidobacterium spp. A review.

Bacteriocins are ribosomally-synthesized antibacterial peptides. These compounds are produced by a broad variety of different bacteria belonging mainly to the genus Bifidobacterium, to which health promoting properties have frequently been attributed. However, despite the fact that the identification of Bifidobacterium-associated bacteriocins was first reported in 1980 and that they exhibit antimicrobial activity against pathogenic microorganisms such as Listeria monocytogenes, Clostridium perfringens, and Escherichia coli, relatively little information is still available about the antimicrobial compounds produced by strains of this genus. More detailed understanding of the action mechanisms of these antimicrobials could allow us to determine the extent to which their production contributes to the probiotic properties of specific bifidobacteria strains and, potentially, be of crucial significance for ultimate preservation of functional foods or pharmaceutical applications. Here we review what is already known about their structure, classification, mode of action, functionality, immunity, production and purification.

Use of lactulose as prebiotic and its influence on the growth, acidification profile and viable counts of different probiotics in fermented skim milk.

Lactulose can be considered as a prebiotic, which is able to stimulate healthy intestinal microflora. In the present work, the use of this ingredient in fermented milk improved quality of skim milk fermented by Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus and Bifidobacterium lactis in co-culture with Streptococcus thermophilus. Compared to control fermentations without lactulose, the addition of such a prebiotic in skim milk increased the counts of all probiotics, with particular concern to B. lactis (bifidogenic effect), the acidification rate and the lactic acid acidity, and concurrently reduced the time to complete fermentation (t(pH4.5)) and the pH at the end of cold storage for 1 to 35 days.