Isolation and Characterization of Microorganisms with Hydrolytic Profile during Anaerobic Digestion and Biogas Production of Cow Dung and Rice Husk

Abstract

Hydrolysis is important to biogas production as it involves breakdown of polysaccharides present in substrates. The Isolation and characterization of bacterial strains with hydrolytic profile during anaerobic digestion of CD (cow dung), RH (rice husk) and their mixture (CD:RH) was the subject of this research .The experiment lasted for 30 days using a 10 litre scale bio-digester. All physico-chemical parameters reduced significantly after digestion for CD (cow dung), RH (rice husk), and CD:RH (cow dung and rice husk) except moisture content that increased in all the substrates. Also, ash content (1.08-1.67 mg) and crude fibre (1.27-1.96 mg) increased in CD only. The pH ranges for the substrates were CD (7.0-7.5), RH (6.1-7.6), and CD:RH (6.1-7.8). Temperature ranges were CD (27.4⁰C-33.5⁰C), RH (27.2⁰C-33.3⁰C) and CD:RH (27.3⁰C-33.4⁰C). The total biogas production of the substrates were, CD (4327.65cm³), RH (100cm³), and CD:RH   (4730.55cm³). Percentage distribution of hydrolytic group of bacteria present in the digester include cellulolytic (37.50%), amylolytic (18.75%) , proteolytic (18.75%) and lipolytic bacteria (25%). Hydrolytic bacteria and fungi isolated were Penicillium notatum, Micrococcus luteus, Pseudomonas aeruginosa, Klebsiella oxytoca, Aspergillus spp, Mucor spp, Bacillus subtilis, Proteus vulgaris, Clostridium spp, Peptostreptococcus spp and Enterobacter aerogene. For hydrolytic groups of bacteria, the following had the highest activities in terms of diameter of cleared zones of inhibition: Amylolytic (Enterobacter spp - 15mm),lipolytic (Pseudomonas spp - 16mm),Cellulolytic (Klebsiella spp - 17mm) and Proteolytic (Pseudomonas spp - 14mm). Rice husk produced the least amount of biogas due to its high cellulose and lignin content. In conclusion, further investigation of hydrolytic groups of bacteria beyond 30 days of anaerobic retention period should be investigated.

Keywords: Hydrolysis, biogas, amylolytic bacteria, lipolytic bacteria, cellulolytic bacteria, proteolytic bacteria