Beta-glucosidase-producing microbial community in response to the carbon catabolite repression during the composting of cattle manure with biochar

Abstract:

[Background] High concentration of glucose will cause carbon catabolite repression, and the functional microbial community producing β-glucosidase adapts to such pressure by differentially regulating the expression of glucose-tolerant and non-glucose tolerant β-glucosidases. Adding biochar in compost can change the environment where microorganisms live and affect the composition and function of the microbial community. [Objective] The effects of biochar addition on the structure and function of β-glucosidase-producing microbial community were analyzed under different carbon metabolism pressures. [Methods] Different carbon metabolism pressures were constructed by adding glucose, cellobiose, and β-glucosidase inhibitor into the biochar-cattle manure-maize straw compost. We used the β-glucosidase gene of the GH1 family derived from bacteria as a molecular marker to construct a gene clone library and measured the activities of carboxymethylc ellulase (CMCase) and β-glucosidase. [Results] Actinobacteria, Proteobacteria, and Bacteroidetes were dominant in the functional microbial community. The relative abundance of Proteobacteria was lower in the low-concentration cellobiose group, and that of Bacteroidetes was significantly higher in the groups with the addition of inhibitor. High glucose significantly inhibited CMCase activity while had little effect on β-glucosidase activity, and low cellobiose markedly induced β-glucosidase activity. The β-glucosidase was activated by high glucose in the high-concentration glucose+high-concentration cellobiose group. [Conclusion] The addition of biochar did not significantly affect the response of the functional microbial community involved in cellulose degradation to carbon catabolite repression. Compared with the natural compost, the addition of biochar in the compost increased the sensitivity of β-glucosidase-producing microbial community to the carbon catabolite repression induced by high concentrations of glucose and to the inductive effect of low-concentration cellobiose.