Anaerobic Digestion of Biodegradable Domestic Wastes by Microorganisms

Abstract

The aim of this study was to demonstrate that biogas can be generated from biodegradable domestic wastes and to determine the bacterial succession involved in the anaerobic decomposition of the wastes. Ten kilogram (10 kg) of biodegradable domestic waste was made into slurry with tap water. The slurry was fed into a batch system biodigester and left at room temperature for 12 weeks. Metagenomic method was used to determine the bacterial and archaeal species involved in the anaerobic digestion. MULTIRAE PGM 50 was used to confirm the presence of the generated biogas from the slurry. Serial dilutions of the slurry was made on alternate days and the appropriate dilutions were inoculated onto nutrient agar plates for bacterial isolation and incubation was at 35°C for 48 hrs. Potato dextrose agar was used for fungal isolation, and incubation was at ambient temperature for three days. Pure isolates of representative communities were maintained on agar slants at 4°C. Triplicate samples from various tubes were cultured and the average count was used. Fungal growth occurred on the PDA plate only on the first day of incubation. The mean total bacteriaial count was highest on the second day (1.3 x107 cfu/ml); it decreased with increasing incubation time and became constant from the 23rd day to the end of the experiment (1.0 x101 cfu/ml). The microorganisms involved in the biodegradation were found to be Lactobacillus rapi strain LA1165, Clostridyum tyrobutyricum, Ralstonia pickettii, Methanoculleus marisnigri, Methanosarcina acetivorans C2A, Clostridium acetobutylicum EA 2018, Clostridium tyrobutyricum 5S, Halothermothrix oremii H168, Lactobacillus rapi strain LA1165, Lactobacillus buchneri, Solobacterium moorei W540, B. vulgatus ATCC8482. Rhizopus spp and Aspergillus spp were isolated only on the first two days of incubation. The result from this study proves that, it is possible to generate biogas from domestic wastes and diverse species of microorganisms are involved in anaerobic digestion of biodegradable domestic wastes.