Protein hydrolysate from organic fraction of municipal solid waste compost as nitrogen source to produce lactic acid by Lactobacillus fermentum ATCC 9338 and Lactobacillus plantarum NCIMB 8826

Can proteins, protein hydrolysates and peptides cooperate with probiotics to inhibit pathogens?

Studies have shown that probiotics can effectively inhibit pathogens in the presence of proteins, protein hydrolysates and peptides (protein derivates). However, it is still unclear the modes of probiotics to inhibit pathogens regulated by protein derivates. Therefore, we summarized the possible effects of protein derivates from different sources on probiotics and pathogens. There is abundant evidence that proteins and peptides from different sources can significantly promote the proliferation of probiotics and increase their secretion of antibacterial substances. Such proteins and peptides can also stimulate the adhesion of probiotics to intestinal epithelial cells and contribute to regulating intestinal immunity, but they seem to have the negative effects on pathogens. Moreover, a direct effect of proteins on intestinal cells is summarized. Whether or not they can cooperate with probiotics to inhibit pathogens using above possible mechanisms were discussed. Furthermore, there seems to be no consistent conclusions that protein derivates have synergistic effects with probiotics, and there is still limited evidence on the inhibiting patterns. Therefore, the existing problems and shortcomings are noted, and future research direction is proposed.

Effect of forest-based biochar on maturity indices and bio-availability of heavy metals during the composting process of organic fraction of municipal solid waste (OFMSW)

The main objective of this study was to investigate the effect of biochar on the composting process of the organic fraction of municipal solid waste (OFMSW) under real conditions. Different doses of biochar (1%, 3%, and 5%) were mixed with compost piles to evaluate the variation of temperature, moisture content (MC), organic matter (OM), carbon (C), nitrogen (N), C/N ratio, and heavy metal (HM) contents in comparison with the control treatment (with 0% biochar addition). The results of this study showed that the compost piles combined with different doses of biochar had higher MC. The use of biochar as an additive, even at low doses (1%), was able to increase the compost quality through the reduction of N losses during the composting process. The highest reduction of OM during the composting process was observed in the control pile (without biochar addition) by 48.06%, whereas biochar affected the biodegradability of OM and prevented the reduction of nutrients during the composting process under real conditions. The contents of HMs (Pb, Zn, Ni, Cd, and Cu) showed a significant reduction in all of the compost piles combined with biochar in comparison with the control treatment. Considering that in terms of all compost quality indicators, the piles combined with biochar can regarded as high standard product, the composts obtained from combining the OFMSW with different biochar doses have desirable features to be used as an amendment agent to improve agricultural soil quality.

Reduced pH is the primary factor promoting humic acid formation during hyperthermophilic pretreatment composting

Hyperthermophilic pretreatment composting (HPC) has the advantages of enhanced composting efficiency and accelerated humic substance (HS) over conventional composting (CC). However, the mechanisms towards the accelerated humification process by HPC are still not clear. By means of sterilization technology, the roles of abiotic and biotic components on the formation of HS can be distinguished. The study investigated the humification degree and the succession of microbial community during HPC of pig manure. The mechanisms underlying the accelerated humification by HPC was identified using gamma sterilization. Results showed that HS content increased significantly by 13.72% in HPC and 29.93% in sterilized HPC inoculated with 1% CC (HPC_I), compared with 8.76% increase in CC and 7.12% increase in sterilized CC inoculated with 1% HPC during composting (CC_I). Compared with CC and CC_I, stronger intensities of HA-like and fulvic acid-like components were observed in HPC and HPC_I. Results showed that physicochemical properties, especially pH, were the key factors in accelerating the humification in HPC, while both physicochemical properties and microbial community contributed to the HA formation in CC. The study contributed to a better understanding of the mechanism towards the accelerated humification degree in HPC.

Identification of soybean peptides and their effect on the growth and metabolism of Limosilactobacillus reuteri LR08

Lactic acid bacteria are one of the most pivotal probiotics. Promoting their viability could be an effective method to modulate the balance of intestinal flora, thereby improving human health. The current solution is to take advantage of carbon-sourced prebiotics, while protein and peptides with potential prebiotic functions have not been investigated. Soy proteins and peptides have been proven to enhance the growth and metabolism of Lactobacillus. However, research on the relationship between strains of lactobacilli and the structure of soybean peptides is still limited. In the present study, soybean protein and peptides effectively increased the growth and organic acid secretion of Limosilactobacillus reuteri LR08. Additionally, soybean peptides and fructooligosaccharides showed synergistic effects in modulating Limosilactobacillus reuteri LR08. Fraction 1 acquired from soy peptides using RP-HPLC exhibited the most effectiveness and several novel peptides were identified. These results could theoretically and practically benefit soybean peptide application as a potential prebiotic.

Resource recovery of lignocellulosic biomass waste into lactic acid - Trends to sustain cleaner production

Biomass waste generation concerns regulatory authorities to develop novel methods to sustain biotransformation processes. Particularly, lactic acid (LA) is a bulk commodity chemical used in diverse industries and holds a growing global market demand. Recently, lignocellulosic waste biomass is preferred for LA bio-production because of its non-edible and inexpensive nature. However, the information about new pretreatment methods for lignocellulosic feedstock, and novel strains capable to produce LA through fermentation is limited. Therefore, this review highlights the advancement of pretreatments methods of lignocellulosic biomass and biotransformation. Herein, we first briefly explored the main sources of lignocellulosic waste biomass, then we explored their latest advances in pretreatment processes particularly supercritical fluid extraction, and microwave-assisted extraction. Approaches for bioconversion were also analyzed, such as consolidated bioprocessing (CBP), simultaneous saccharification and fermentation (SSF), separate hydrolysis fermentation (SHF), among other alternatives. Also, new trends and approaches were documented, such as metagenomics to find novel strains of microorganisms and the use of recombinant strategies for the creation of new strains. Finally, we developed a holistic and sustainable perspective based on novel microbial ecology tools such as next-gen sequencing, bioinformatics, and metagenomics. All these shed light on the needs to culture powerful microbial isolates, co-cultures, and mixed consortia to improve fermentation processes with the aim of optimizing cultures and feedstock pretreatments.