Improved Short-Chain Fatty Acids Production and Protein Degradation During the Anaerobic Fermentation of Waste-Activated Sludge via Alumina Slag-Modified Biochar.

As the by-product in the biological sewage treatment, waste-activated sludge (WAS) always suffers from the difficulty of disposal. Anaerobic fermentation to achieve valuable carbon sources is a feasible way for resource utilization of WAS, whereas the process is always restricted by its biochemical efficiency. Hence, the WAS was used as the feedstock in this study. Alumina slag-modified biochar (Al@BioC) respectively from pine wood (PW) or fresh vinegar residue (FVR) was employed to stimulate the process of short-chain fatty acids (SCFAs) production during the anaerobic treatment of WAS. The results indicate that the addition of Al@BioC could facilitate the distinct increase in SCFAs yield (42.66 g/L) by 14.09% and acetate yield (33.30 g/L) by 18.77%, respectively, when compared with that in regular fermentation without Al@BioC addition. Furthermore, protein degradation was also improved. With the Al@BioCPW added, the maximum concentration of soluble protein reached 867.68 mg/L and was 24.39% higher than the initial level, while the enhancement in the group with Al@BioCFVR and without biochar addition was 12.49% and 7.44%, respectively. According to the results of 16S rDNA sequencing, the relative abundance of acid-producing bacteria (Bacteroidota and Firmicutes) was enriched, enhancing the pathways of protein metabolisms and the ability to resist the harsh environment, respectively. Moreover, Proteiniphilum under Bacteroidota and Fastidiosipila under Firmicutes were the main microorganisms to metabolize protein. The above results might provide a novel material for harvesting the SCFAs production, which is conducive to harmless disposal and carbon resource recovery.

Isolation and identification of a novel erythromycin-degrading fungus, Curvularia sp. RJJ-5, and its degradation pathway.

Erythromycin pollution is an important risk to the ecosystem and human health worldwide. Thus, it is urgent to develop effective approaches to decontaminate erythromycin. In this study, we successfully isolated a novel erythromycin-degrading fungus from an erythromycin-contaminated site. The erythromycin biodegradation characteristics were investigated in mineral salt medium with erythromycin as the sole carbon and energy source. The metabolites of erythromycin degraded by fungus were identified and used to derive the degradation pathway. Based on morphological and phylogenetic analyses, the isolated strain was named Curvularia sp. RJJ-5 (MN759651). Optimal degradation conditions for strain RJJ-5 were 30°C, and pH 6.0 with 100 mg L-1 erythromycin substrate. The strain could degrade 75.69% erythromycin under this condition. The following metabolites were detected: 3-depyranosyloxy erythromycin A, 7,12-dyhydroxy-6-deoxyerythronolide B, 2,4,6,8,10,12-hexamethyl-3,5,6,11,12,13-hexahydroxy-9-ketopentadecanoic acid and cladinose. It was deduced that the erythromycin A was degraded to 3-depyranosyloxy erythromycin A by glycoside hydrolase in the initial reaction. These results imply that Curvularia sp. RJJ-5 is a novel erythromycin-degrading fungus that can hydrolyze erythromycin using a glycoside hydrolase and has great potential for removing erythromycin from mycelial dreg and the contaminated environment.