Biodegradation study of PDLA/cellulose microfibres biocomposites by Pseudomonas aeruginosa

Carbohydrate based biostimulation regulates the structure, function and remediation of Cr(VI) pollution by SRBs flora

Sulfate reducing bacteria (SRBs) have promising applications as important microorganisms in the microbial approach to remediation of soil heavy metal pollution. However, fewer studies have been conducted on the differences in community structure, community function, heavy metal remediation capacity and effects with SRBs cultured from different carbohydrate. In this study, we investigated the structure and function of different SRBs flora, the reduction mechanism of Cr(VI) and remediation effect on Cr(VI) contaminated soil through high throughput sequencing, ICP-OES analysis and a series of soil remediation experiments. The results showed that there were significant differences in the community structure and function of SRBs flora cultured with different carbohydrate, and glycerine cultivated community with high SRBs abundance, diverse community structure, complete community function, which realizing the best SRBs flora performance. This SRBs flora under the optimal carbon/sulfur ratio, Fe(II), and sodium chloride conditions of 2, 50-500 mg/L, and 0-2.5 %, respectively and the highest sulfate and Cr(VI) reduction rates reached 84.2 % and 73.6 %, respectively, which the hydrogen sulfide pathway was the dominant pathway for Cr(VI) reduction. The SRBs flora cultured with glycerine, lactate, and butyrate obtained a good community structure sulfate and Cr(VI) reduction rates in contaminated soils, which the restored seed germination function and significantly blocked the migration of Cr(VI) into plants. The study provides new technical idea to regulate the structure and function of SRBs flora by means of selecting carbohydrate for the efficient remediation of soil Cr(VI) pollution.

Biodegradation of DDT using multi-species mixtures: From genome-mining prediction to practical assessment

DDT (dichlorodiphenyltrichloroethane) is a commonly used insecticide that is recalcitrant and highly stable in the environment. Currently, DDT residue contamination, especially in agricultural soil, is still a concern in many countries, threatening human health and the environment. Among the approaches to resolve such an issue, novel biodegradation-based methods are now preferred to physicochemical methods, due to the sustainability and the effectiveness of the former. In this study, we explored the possibility of building mixed microbial cultures that can offer improved DDT-degrading efficiencies and be more environmentally transilient, based on genome annotation using the KEGG database and prediction of interactions between single strains using the obtained metabolic maps. We then proposed 10 potential DDT-degrading mixed cultures of different strain combinations and evaluated their DDT degradation performances in liquid, semi-solid and solid media. The results demonstrated the superiority of the mixtures over the single strains in terms of degrading DDT, particularly in a semi-solid medium, with up to 40-50% more efficiency. Not only did the mixed cultures degrade DDT more efficiently, but they also adapted to broader spectra of environmental conditions. The three best DDT-degrading and transilient mixtures were selected, and it turned out that their component strains seemed to have more metabolic interactions than those in the other mixtures. Thus, our study demonstrates the effectiveness of exploiting genome-mining techniques and the use of constructed mixed cultures in improving biodegradation.

Accelerated degradation of cellulose in silkworm excrement by the interaction of housefly larvae and cellulose-degrading bacteria

The environmental pollution caused by silkworm (Bombyx mori) excrement is prominent, and rich in refractory cellulose is the bottleneck restricting the efficient recycling of silkworm excrement. This study was performed to investigate the effects of housefly larvae vermicomposting on the biodegradation of cellulose in silkworm excrement. After six days, a 58.90% reduction of cellulose content in treatment groups was observed, which was significantly higher than 11.5% of the control groups without housefly larvae. Three cellulose-degrading bacterial strains were isolated from silkworm excrement, which were identified as Bacillus licheniformis, Bacillus amyloliquefaciens, and Bacillus subtilis based on 16S rRNA gene sequence analysis. These three bacterial stains had a high cellulose degradation index (HC value ranged to between 1.86 and 5.97 and FPase ranged from 5.07 U/mL to 7.31 U/mL). It was found that housefly larvae increased the abundance of cellulose-degrading bacterial genus (Bacillus and Pseudomonas) by regulating the external environmental conditions (temperature and pH). Carbohydrate metabolism was the bacterial communities' primary function during vermicomposting based on the PICRUSt. The results of Tax4Fun indicated that the abundance of endo-β-1,4-glucanase and exo-β-1,4-glucanase increased rapidly and maintained at a higher level in silkworm excrement due to the addition of housefly larvae, which contributed to the accelerated degradation of cellulose in silkworm excrement. The finding of this investigation showed that housefly larvae can significantly accelerate the degradation of cellulose in silkworm excrement by increasing the abundance of cellulose-degrading bacterial genera and cellulase.

Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments

Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment's factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO2 evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed.

Advances in Cellulose-Based Hydrogels for Biomedical Engineering: A Review Summary

In recent years, hydrogel-based research in biomedical engineering has attracted more attention. Cellulose-based hydrogels have become a research hotspot in the field of functional materials because of their outstanding characteristics such as excellent flexibility, stimulus-response, biocompatibility, and degradability. In addition, cellulose-based hydrogel materials exhibit excellent mechanical properties and designable functions through different preparation methods and structure designs, demonstrating huge development potential. In this review, we have systematically summarized sources and types of cellulose and the formation mechanism of the hydrogel. We have reviewed and discussed the recent progress in the development of cellulose-based hydrogels and introduced their applications such as ionic conduction, thermal insulation, and drug delivery. Also, we analyzed and highlighted the trends and opportunities for the further development of cellulose-based hydrogels as emerging materials in the future.