Physiological, Biochemical Characteristics And Degradation Properties Of Thermophilic Bacteria

Thermophilic bacteria have gained much attention for its unique genetic types and physiological mechanism and its metabolic enzymes have good acid and alkali-resistant, heat resistant and harmful substance resistant properties. However, studies on Biotransformation and metabolism control of thermophiles are deficient, which hinder promotion of biodegradation and technological advancement of food waste. In this study, four thermophilic bacteria degrading wide range of organic substrates and four cellulose-decomposing thermophiles were investigated for physiological characteristics and their capability of organic degradation. Composite microbial system decomposing wide range of organic substrates was also established initially in order to pave the way of research on collaborative enzyme production mechanism and metabolism control of microbial system to promote microbial degradation of food wastes. Results are as follows:(1) Four thermophilic bacteria Y5, Y6, L3 and L5 isolated at 65℃with wide degrading range of organic substrates were studied for their physiological characteristics. Results showed that Y5 and L3 with capsule but no motility were gram-negative facultative anaerobes, and Y6 and L5 with capsule but no motility were gram-positive facultative anaerobes. These strains Y5, Y6, L3 cannot generate oxidase but catalase. Only L5 can generate oxidase and catalase. For growth of the four strains, optimum temperature range was 60℃-65℃and optimum range of pH value was 6.0-9.0. They all can utilize a wide range of carbohydrates as carbon source, including glucose, fructose, trehalose and soluble starch, but cannot use CMC-Na, lactose and mannitol. And sucrose can be utilized by Y5, L3 and L5. According to 16S rDNA sequence analysis, they belonged to Geobacillus sp.(2) Physiological characteristics of four cellulose-decomposing thermophiles (C1,C2,C3 and C4) isolated at 70℃were investigated. Results showed that C1,C2 and C3 had capsule while C4 had no capsule. The four strains were all aerobic rod-shaped bacteria, and can produce oxidase and catalase. Catalase activity of C1 and C2 were higher than that of the other two strains. The four strains can generate cellulase.C3 and C4 had better capability of cellulose degradation than C1 and C2. Synergy had been found between C1 and C2, Cl and C3, and C1,C2 and C3. Cellulose degradation by C3 started more slowly than that by the other three stains. However, C3 grew better than the others in the liquid medium with cellulose as a sole carbon source.(3) Composite microbial system decomposing wide range of organic substrates was also conducted initially by eight groups from A-G and A-1. After domestication, the degradation efficiency order of soluble starch was F>E>A>A-1, the degradation efficiency order of filter paper was F>E> A-1> A, and the degradation efficiency order of protein was E>F>A>A-1. Group E had best degradation of protein. The OD of fat increased instead of decrease since fat emulsified at high temperature. This obstructed the evaluation of ability of fat degradation by composite microbial system. And much research was needed on the effect of high temperature on fat degradation.