Characterization of acidogenesis occurring on rainbow trout (Oncorhynchus mykiss) sludge by indigenous Alcaligenes faecalis

Deep exploitation of refractory organics in anaerobic dynamic membrane bioreactor for volatile fatty acids production from sludge fermentation: Performance and effect of protease catalysis

Volatile fatty acids (VFAs) production from waste activated sludge fermentation could be improved in anaerobic dynamic membrane bioreactor (ADMBR) by retaining residual organics within the reactor and prolonging their reaction time. However, the accumulation of refractory organics made it operate unstably. Therefore, protease catalysis was adopted to deeply exploit those refractory organics in sludge. By combining with dynamic membrane retention, protease catalysis indeed presented a good performance. VFAs yield was further enhanced by over 40% in ADMBR. Membrane fouling was slightly relieved due to protein and polysaccharide degradations in the sludge of dynamic membrane. It was also interestingly found that not only protease activity of sludge was improved from 5 to 21 U/ml, but also β-GLC activity was enhanced from 13 to 20 μmoL/L/h. Microbial community analysis showed protease addition could reduce bacterial richness and evenness in sludge, and accelerate the growth of polysaccharides-hydrolyzing bacteria, as well as inhibit some proteolytic bacteria.

Role of acid/alkali-treatment in primary sludge anaerobic fermentation: Insights into microbial community structure, functional shifts and metabolic output by high-throughput sequencing

This study aimed to investigate the effect of acid- or alkali-treatment on volatile fatty acids (VFAs) production and microbiological mechanism during primary sludge anaerobic fermentation. Seven fermentation experiments were conducted at different pH (3-12). Results showed that the optimal pH was 10 for accumulation of VFAs. High-throughput sequencing results indicated that acid and alkali treatment could inhibit Erysipelotrichaceae_UCG-004 and norank_p_Aminicenantes, instead of promoting Pseudomonas and Tissierella at acidic and alkaline condition, respectively. Besides, molecular ecological networks (MENs) analysis and multivariate canonical correspondence analysis (CCA) revealed that the microbial community interactions are significant different between acid and alkali treatment groups, and acetic acid was the most vital factor in the distinct bacterial community assemblages. Predictive functional profiling using marker gene sequences found that amino acid transport and metabolism was the most abundant metabolic type with 8.43-9.41%, and acid- and alkali-treatment did not benefit Stickland reaction.