Study On Enzyme Activity And Decomposition Products In Hydrolysis Of Kitchen Garbage

The yield of kitchen garbage is huge, and with an increasing trend. It is very important to find an efficient method to deal with kitchen garbage. Kitchen garbage is rich in starch, protein, fat, cellulose, and other organic substances. It is nutrient-rich and highly biodegradable. Microorganisms hydrolyze organic matter of kitchen garbage to produce reducing sugar, free amino acid(FAA), phosphate, nitrate and so on. The efficiency treatment of kitchen garbage not only can relieve pressure on the environment, but also can achieve purposes of kitchen garbage recycling.The present study was conducted with Aspergillus niger screened from the soil and Backusella circina preserved in the laboratory, two strains with different preferences of decomposition for starch and protein. We studied the effects of sterilization of fermentation medium and the process of aseptic operation、different inoculation orders and initial total solid concentration of kitchen garbage on hydrolysis process of the garbage. In the process of hydrolysis, characteristics of the garbage indicators including pH, yield of reducing sugar and FAA and the activity of amylase and protease were studied.The results showed the sterilization pretreatment produced higher yield of reducing sugar and FAA than the one without sterilization pretreatment. In the same pretreatment, subsequent operation under sterile treatments had little effect on the yield of reducing sugar and FAA. Different inoculation orders of fungi have significant effects on yield of reducing sugar after 48h of FAA after 96h of fermentation. The treatment, first inoculated with Backusella circina for 24h followed by addition of Aspergillus niger, produced maximum yield of reducing sugar and FAA. At the optimum initial total solid concentration of 2.5%, fungi produced maximal amylase of 382.4 U/mL and protease of 212.3 U/mL. When initial total solid concentration was from 1.25% to 10%, the yield of reducing sugar and FAA increased linearly with increasing initial weight of kitchen garbage:with increase by per percent of initial total solid concentrations, adding 1.14g reducing sugar and 11.38mg FAA, respectively.