Impacts of microplastic type on the fate of antibiotic resistance genes and horizontal gene transfer mechanism during anaerobic digestion.

Microplastics (MPs) and antibiotic resistance genes (ARGs) are important pollutants in waste activated sludge (WAS), but their interactions during anaerobic digestion (AD) still need to be further explored. This study investigated variations in ARGs, mobile genetic elements (MGEs), and host bacteria during AD under the pressure of polyamide (PA), polyethylene (PE), and polypropylene (PP). The results showed that the MPs increased methane production by 11.7-35.5%, and decreased ARG abundance by 5.6-24.6%. Correlation analysis showed that the decrease of MGEs (plasmid, prophage, etc.) promoted the decrease of the abundance of multidrug, aminoglycoside and tetracycline resistance genes. Metagenomic annotation revealed that the reduction of key host bacteria (Arenimonas, Lautropia, etc.) reduced the abundance of major ARGs (rsmA, rpoB2, etc.). Moreover, PP MPs contributed to a reduction in the abundance of functional genes related to the production of reactive oxygen species, ATP synthesis, and cell membrane permeability, which was conducive to reducing the potential for horizontal gene transfer of ARGs. These findings provide insights into the treatment of organic waste containing MPs.

Organic acids drove the microbiota succession and consequently altered the flavor quality of Laotan Suancai across fermentation rounds: Insights from the microbiome and metabolome.

Laotan Suancai, a popular traditional Chinese fermented vegetable, is manufactured in the industry via four fermentation rounds. However, the differences in flavor quality of Laotan Suancai from the four fermentation rounds and the causes of this variation remain unclear. Metabolome analysis indicated that the different content of five taste compounds and 31 aroma compounds caused the differences in flavor quality among the variated fermentation rounds of Laotan Suancai. Amplicon sequencing indicated that the microbial succession exhibited a certain pattern during four fermentation rounds and further analysis unveiled that organic acids drove the microbiota shift to more acid-resistant populations. Spearman correlation analysis highlighted that seven core microbes may be involved in the formation of differential flavor and the corresponding metabolic pathways were reconstructed by function prediction. Our findings offer a novel perspective on comprehending the deterioration of flavor quality across the fermentation rounds of Laotan Suancai.

Two-stage fermentation of corn and soybean meal mixture by Bacillus subtilis and Lactobacillus acidophilus to improve feeding value: optimization, physicochemical property, and microbial community.

Microbial treatment can reduce the antinutritional factors and allergenic proteins in corn-soybean meal mixture (CSMM), but the role of the microbial community in hypoallergenicity and digestibility during the fermentation process remains unclear. Therefore, the fermentation strains of Bacillus and LAB were determined, and the compatibility and fermentation process of two-stage solid fermentation composite bacteria were optimized, and the dynamic changes in physicochemical property and microbial community during two-stage fermentation were investigated. Results showed that Bacillus subtilis NCUBSL003 and Lactobacillus acidophilus NCUA065016 were the best fermentation combinations. The optimal fermentation conditions were inoculum 7.14%, solid-liquid ratio of 1:0.88 and fermentation time of 74.30 h. The contents of TI, ß-conglycinin and glycinin decreased significantly after fermentation. Besides, TCA-SP, small peptides and FAA increased. Bacillus and Lactobacillus were the main genera. Pathogenic bacteria genera were inhibited effectively. This study suggests the feasibility of two-stage fermentation in improving the nutrient values and safety of the CSMM. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-023-01426-7.

Effects of fermentation with Lactiplantibacillus plantarum NCU116 on the antihypertensive activity and protein structure of black sesame seed.

Effects of fermentation by Lactobacillus Plantarum NCU116 on the antihypertensive potential of black sesame seed (BSS) and structure characteristics of fermented black sesame seed protein (FBSSP) were investigated. Angiotensin-I-converting enzyme (ACE) inhibition and zinc chelating ability of fermented black sesame seed hydrolysate (FBSSH) reached the highest of 60.78 ± 3.67 % and 2.93 ± 0.04 mg/mL at 48 h and 60 h of fermentation, respectively. Additionally, the antioxidant activities of FBSSH and surface hydrophobicity of FBSSP were increased noticeably by fermentation. The α-helix and ß-rotation of FBSSP tended to decrease and increase, respectively, during fermentation. Correlation analysis indicated strong positive relationships between ß-turn and ACE inhibition activity as well as zinc chelating ability with correlation coefficients r of 0.8976 and 0.8932. Importantly, novel ACE inhibitory peptides LLLPYY (IC50 = 12.20 µM) and ALIPSF (IC50 = 558.99 µM) were screened from FBSSH at 48 h using in silico method. Both peptides showed high antioxidant activities in vitro. Molecular docking analysis demonstrated that the hydrogen bond connected with zinc ions of ACE mainly attributed to the potent ACE inhibitory activity of LLLPYY. The findings indicated that fermentation by Lactobacillus Plantarum NCU116 is an effective method to enhance the antihypertensive potential of BSS.

Integrated metatranscriptomics and metabolomics reveal microbial succession and flavor formation mechanisms during the spontaneous fermentation of Laotan Suancai.

Laotan Suancai, a Chinese traditional fermented vegetable, possesses a unique flavor that depends on the fermentative microbiota. However, the drivers of microbial succession and the correlation between flavor and active microbiota remain unclear. A total of 21 characteristic flavor metabolites were identified in Laotan Suancai by metabolomics, including 8 sulfides, 6 terpenes, 3 organic acids, 2 isothiocyanates, 1 ester, and 1 pyrazine. Metatranscriptome analysis revealed variations in the active microbiota at different stages of fermentation, and further analysis indicated that organic acids were the primary drivers of microbial succession. Additionally, we reconstructed the metabolic network responsible for the formation of characteristic flavor compounds and identified Companilactobacillus alimentarius, Weissella cibaria, Lactiplantibacillus plantarum, and Loigolactobacillus coryniformis as the core functional microbes involved in flavor development. This study contributed to profoundly understanding the relationship between the active microbiota and flavor quality formation, as well as the targeted selection of starters with flavor regulation abilities.

Effects of enzyme treatment on the antihypertensive activity and protein structure of black sesame seed (Sesamum indicum L.) after fermentation pretreatment.

Effects of enzyme treatment on the hypertensive potential and protein structure of black sesame seed (BSS) were investigated. Compared with BSS, Angiotensin-converting enzyme (ACE) inhibition of fermented black sesame seed (FBSS) has significantly improved after acid protease processing and reached 75.39% at 2 U/g in 3 h. Meanwhile, the zinc chelating ability and antioxidant activity of FBSS hydrolysate as well as surface hydrophobicity, free sulfhydryl content, and peptide content of FBSS protein, were significantly increased. The results illustrated that this strategy promoted the protein unfolding and exposure of hydrophobic residues, thus contributing toward enzymatic hydrolysis. Secondary structure results indicated that the α-helix of FBSS protein and ß-sheet of BSS protein decreased after hydrolyzing. The differences in ACE inhibition may also result from the difference in peptide sequence except for peptide content. In conclusion, the combination of fermentation pretreatment and enzyme treatment is an effective method to enhance the antihypertensive potential of BSS.