Dietary supplementation with probiotics has been demonstrated to enhance nutritional efficiency and economic traits in the silkworms (Bombyx mori), with mechanistic insights indicating that these benefits are associated with gut microbiota activity and mucosal immune modulation through the regulation of enzymatic functions. This study investigated the effects of probiotic Bacillus species on intestinal microbiome diversity in fifth-instar silkworms. Two native isolates, Bacillus subtilis Y11 and Bacillus velezensis Z55, were administered either individually or in combination to experimental groups (CK, Y11, Z55, and Y11/Z55) on the first day of the fifth instar. Intestinal contents were collected at days 1, 3, and 5 after treatment for 16S rRNA gene sequencing, and cellulose content in silkworm excrement was measured on a daily basis. Experimental groups exhibited significantly elevated body weight, digestive capacity, and cocoon weight compared to controls. The cellulose content in silkworm excrement decreased by 24.7% and 31.8% on days 2 and 3, respectively, compared to the control (CK) group at the corresponding time points. Tax4Fun2 analysis further predicted a rapid increase in the potential abundance of cellulose degradation-related genes within the gut microbiome, an inference based on taxonomic composition. These findings support the hypothesis that probiotic treatment may enhance the net efficiency of cellulose degradation in silkworms by modulating the gut microbial community and structure, thereby offering new insights into improving their growth performance.

An abundance of refractory cellulose is the key limiting factor restricting the resource utilization efficiency of silkworm (Bombyx mori) excrement via composting. Screening for cellulose-degrading bacteria is likely to provide high-quality strains for the safe and rapid decomposition of silkworm excrement. In this study, bacteria capable of degrading cellulose with a high efficiency were isolated from silkworm excrement and the conditions for cellulase production were optimized. The strains were preliminarily screened via sodium carboxymethyl cellulose culture and staining with Congo red, rescreened via a filter paper enzyme activity test, and identified via morphological observation, physiological and biochemical tests, and phylogenetic analysis of the 16S rDNA sequence. Enzyme activity assay was performed using the 3,5-dinitrosalicylic acid method. DC-11, a highly cellulolytic strain, was identified as Bacillus subtilis. The optimum temperature and pH of this strain were 55 °C and 6, respectively, and the filter paper enzyme activity (FPase), endoglucanase activity (CMCase), and exoglucanase activity (CXase) reached 15.40 U/mL, 11.91 U/mL, and 20.61 U/mL. In addition, the cellulose degradation rate of the treatment group treated with DC-11 was 39.57% in the bioaugmentation test, which was significantly higher than that of the control group without DC-11 (10.01%). Strain DC-11 was shown to be an acid-resistant and heat-resistant cellulose-degrading strain, with high cellulase activity. This strain can exert a bioaugmentation effect on cellulose degradation and has the potential for use in preparing microbial inocula that can be applied for the safe and rapid composting of silkworm excrement.

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.

Lipase Novozym 435 was used as catalyst to degrade P(BS-co-DGS), which was a kind of PBS-based copolyester modified with diethylene glycol (DEG), in a THF/toluene mixed solvent system. P(BS-co-DGS) copolyesters were synthesized by copolymerization and characterized by 1H NMR. GPC and TGA were used to investigate average molecular weight and thermal property before and after degradation, respectively. After degraded by N435 for 30 h, the Mn of P(BS-co-DGS)10 (DEG content 10%) decreased from 8.33×104 to 3.52×104 g·mol-1 with some yellow oil droplets of oligomers appearing. And the initial decomposition temperature (the temperature at 5% mass loss) of P(BS-co-DGS)10 changed from 300.6 to 178.9. MALDI-TOF-MS results showed that none of DEG oligomers appeared in P(BS-co-DGS)10 degradation products. However, when the DEG content increased to 20%, there were the DEG circle oligomers as well as linear oligomers in the degradation products.

Streptomyces diastatochromogenes TUST2, which was isolated from Hainan province, produced the antimicrobial poly( amino acid), epsilon-poly-L-lysine. In this study, the epsilon-poly-L-lysine-degrading enzyme was purified from this strain and its properties of this enzyme were determined. Preliminary data suggested that the epsilon-poly-L-lysine-degrading enzyme was a cell membrane associated protein. To extract this enzyme, bacterial cells were collected and disrupted with an ultrasonic oscillator, the membrane fraction were solubilized with 1.0 mol/L NaSCN solution. The coarse enzyme extraction was subjected to Sephadex G100 column for purification. With 100 mmol/L phosphate buffer as elution solution, the fractions with the enzyme activity were collected. The purified sample was analyzed with SDS-PAGE and the subunit molecular mass of the enzyme was estimated to be about 54700. The enzyme was stable between pH 6.0 kind 9.0, with a maximum at pH = 7.0. The optimum temperature was 30 degrees C, and no significant activity loss was observed when the enzyme was incubated at 10-50 degrees C for 30 min. The effect of different metal ions on the activity of the enzyme were also investigated, some metal ions, including Zn2+, Fe3+, and Cu2+, could increase the enzyme activities by 29.72%, 15.85%, and 15.08%, respectively; while some other metal ions, including Ag+, Hg2+, Co2+ and Mn2+, strongly inhibited the enzyme activity. The enzyme activity was not affected by Ca2+, K+ and Ba2+. Experiment results also showed that the enzyme activity increased 10% by addition of 4% Tween-80, while EDTA strongly inhibited the enzyme activity. These results suggested that the specificities of this enzyme are similar to that of the epsilon-poly-L-lysine-degrading enzyme from streptomyces albulus.

Owing to the insolubility of the binary phase system for oxidative desulfurization, a formic acid/H2O2 system with quaternary ammonium salts as phase-transfer catalysts was employed in the oxidation of thiophene. Four catalytic systems with ultrasound were carried out, tetrabutyl ammonium bromide behaved as the optimum active catalyst, and the desulfurization rate was 94.67%. Dispersion of phase-transfer catalyst between the organic and aqueous phases was related to the extraction constant. When the amount of catalyst exceeded 0.0019 mol L-1, quaternary ammonium salts would serve well to transfer the polar substance of oxidant [HCOOO-] to the nonpolar environment of the organic phase. In the transfer process, complexation [HCOOO-Q-X] resulted from the interaction of oxidant and phase-transfer catalyst, which could decrease the polarity of the oxidant and the apparent activation energy. With the extractive equilibrium and oxidative reaction, a dynamic model was developed. From the study of kinetics, it could be shown that the reaction order was pseudo-first-order.