Isolation and identification of microbes to convert green wastes to sugars for ethanol production

• Main Author: Lim, Si Jia.
• Other Authors: Wang Jing-Yuan
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/16153
• Institution: Nanyang Technological University

The function of the microorganisms in the intestinal tracts of certain species of insects has attracted the interest of many researchers. In this study, bacterial communities which played the key physiological function in cellulose and hemicellulose digestion within the guts of the larvae of the yellow mealworm, Tenebrio molitor L. were investigated. With the current booming concerns in the economic and environmental issues, low-cost ethanol produced from cellulose biomass provided a better alternative in replacing the consumption of fossil fuel. This study was essential in identifying those high-efficiency lignocelluloses-degrading microorganisms so as to cut down the usage of high-cost commercial enzymes in ethanol production. Two types of culture mediums (M1 and M2) with different nutritional level were selected to cultivate the desired microorganisms from the guts of T.molitor under aerobic condition. Lignocelluloses, filter paper and carboxymethyl cellulose (CMC) were used as the cellulose sources in the medium to investigate enzymatic activity of the microorganisms in degrading these sources to reducing sugar in which the concentration was determined using Dinitrosalisylic acid method. A daily observation on the pH and turbidity conditions was taken to detect the presence of the growth of microbes in the mediums. DNA was extracted from each batch of cultivation and being amplified using PCR so that the microbial community could be identified through the denaturing process using Denaturing Gradient Gel Electrophoresis (DGGE). Through the experimental results obtained, enzymatic activity for the cellulose-degrading microorganisms was higher in M2 as compared to M1. Higher concentration of reducing sugars and the percentage of conversion for total sugars was achieved in M2. DGGE profiles also exhibited larger bacteria population in M2. This was due to the various salts such as Phosphate, Magnesium and sulfur which enriched the bacterial growth.