Cellulose Degradation Microorganisms and Environmental-Friendly Solution to the Agricultural Waste Management

Agricultural waste is a general term for all agricultural residues. Comprehensively, agricultural waste refers to the organic residues in agricultural activity, which includes multiple crop straws, animal and human excreta, kitchen wastes, and industrial or agricultural processing residues. For a long time, agricultural waste, namely, inedible parts of plants, has been mainly used to be raw materials for the preparation of feed, fuel, and compost. Due to the low nutrition, low calorific value, and refractory residues, agricultural wastes currently have become the abandoned agricultural wastes. However, with the progress of modern biotechnology, the so-called wastes are starting to be shown the practice value, particularly in the fields of organic agriculture and bioenergy. Cellulose, an insoluble polymer composed of long chains of β-1,4-linked glucose residues associated in microfibrils, is the major component of plant biomass and the most abundant organic compound in the biosphere. Plant cellulose can be degraded to soluble sugars by synergistic mixtures of microbial cellulases and other cell wall-degrading enzymes and is becoming an important renewable source for biofertilizer and bioenergy production. In recent years, progress has been made in isolating and identifying multifunctional cellulose degradation microorganisms and degrading enzymes. Due to the complexity of straw cellulose structure and fermentation process, the highly efficient degradation of cellulose requires synergistic interactions of varieties of microorganisms. In addition, during microbial fermentation, the condition in fermentation system is extreme. Microorganisms must have the ability to adapt to the extreme environments in order to maintain the continuous fermentation. Therefore, extreme environmental microorganisms have become the urgent chosen for fermentation. In this chapter, we will focus on the four aspects: (1) isolation and identification of cellulose-degrading microorganisms, (2) the degradation mechanism of cellulose by microorganisms and cellulase system, (3) synergistic mechanism of varieties of microorganisms, and (4) biofertilizer and bioenergy application.