Microbial succession of lignocellulose degrading bacteria during composting of corn stalk.

The discarding and burning of corn stalks in the fields after harvesting lead to environmental pollution and waste of resources. Composting is an effective way to disposal of the crop straws. Composting is a complex biochemical process and needs a detailed study in cold region. Hence, the succession process of bacteria and Actinomycetes in the process of corn stalk composting in cold region was studied by 16SrRNA. Alpha diversity analysis showed that the detection results could represent the real situation. The bacterial community diversity from high to low was F50 > F90 > F0 > F10 > F20. The results of beta analysis showed that F20 and F50 had the most similar microbial structure at the phylum level, and the difference between F0 and F20 was the largest. The dominant microbes changed from Proteobacteria and Bacteroidetes in F0 in heating stage to Firmicutes and Proteobacteria, Actinobacteria and Firmicutes in F10 during early high temperature stage, and Actinobacteria, Proteobacteria and Bacteroidetes in cooling and post composting phases. Actinobacteria and Firmicutes were the dominant bacteria in the whole composting process. In the composting process, the microbial community was mainly involved in amino acid metabolism related to nitrogen transformation and carbohydrate metabolism related to lignocellulose degradation. Lignin and hemicellulose were mainly degraded in thermophilic stage. The conversion of nitrogen and degradation of cellulose occurred mainly in the early stages of composting. The research will be helpful to understand the biochemical process of composting in cold region.

Evaluation of lignin inhibition in anaerobic digestion from the perspective of reducing the hydrolysis rate of holocellulose.

In this study, Anaerobic Digestion Model No. 1 (ADM1) were modified to simulate anaerobic digestion (AD) process of microcrystalline cellulose (MCC) and five lignocellulosic substrates, with the goal of predicting the hydrolysis rates of holocellulose fractions in environments with and without lignin inhibition. After model verification, the hydrolysis rate constant of MCC, i.e., the hydrolyzability of cellulose without lignin inhibition, was 3.227 d-1, while those of the holocellulose fractions of five lignocellulosic substrates (I_khyd) were in the range of 1.270 d-1 to 3.364 d-1 (average of 2.242 d-1), which demonstrated remarkable suppression of holocellulose hydrolysis by lignin. Lignin inhibition index (LII) was proposed as an indicator to intuitively quantify and characterize the lignin inhibitory strength in a specific substrate. A series of factors with the potential to affect the LII were analyzed sequentially. This study provides an advanced understanding of the participation and behavior of lignin in the AD process.