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Biogas is anaerobic degradation product formed from aqueous slurry of organic waste in a digester. It can be produced from cattle dung,(cd)chicken droppings, decaying leaves, kitchen waste foods(kwf), sewage sludge, slaughter house, goat, pig or sheep manure, Aqueous slurry of 200g/L of mixed or single substrate of cattle dung or/and kitchen waste evolved up to 400mL of biogas at ambient temperatures. The rate of gas evolution reached 5mL/day on the 15th day using 25% cd mixed slurry. The rates of degradation attained in the mixtures were 1.42ml/g for cd; 1.58mL/g for kwf; 1.78mL/g for 75% cd mixed substrate; 1.78mL/g for 50% cd mixed substrate; 1.92mL/g for 25% cd mixed substrate slurries. The comparative rate of biogas formation ranged from1.25 to 1.35 which was in agreement with the range published in literature of 0.8 to 5.5. Biogas can be synthesized efficiently at ambient temperature in Kampala as was done at mesophilic temperatures elsewhere. However, it may be necessary to attempt producing biogas at different pH and temperatures as well as using other substrates and inoculums.
The agricultural organic wastes pose major environmental issues and their inappropriate disposal is a major cause of pollution while these as cheap lignocellulosic resources can be utilized for many value added products such as enzymes. The purpose of the present study was to utilize wheat bran as a sole substrate for enhanced cellulase production under submerged fermentation (SMF) or solid state fermentation (SSF) and optimize the various process variables involved in the selected fermentation type. In order to achieve high titer of cellulase, a central composite design (CCD) was constructed and performed for optimization of SSF with five process variables at five coded levels. A 25 full factorial design was constructed leading to a set of 50 experiments that were performed in triplicates. The key variables namely incubation time, temperature, wheat bran and tap water ratio, pH and inoculum size were evaluated. The optimization of the process variables resulted in 1.14 IU/ml of cellulase activity from Bacillus subtilis PJK6 under SSF using wheat bran as a sole organic substrate with tap water. The optimum conditions included incubation time- 72 h, temperature- 45oC, pH- 6, inoculum size- 14% with 1:4 as wheat bran and tap water ratio. The production of cellulase using only moistened wheat bran was demonstrated and found to be significantly controlled by incubation time and temperature while pH showed the least effect. The economic production of valuable and useful enzyme using agricultural residue was achieved at moderate conditions from a GRAS microbe that can benefit the industry as well as the environment.
Nigeria is the world leading producer of cassava. During processing of gari from cassava tuber large volume of effluents are discharged in the environment which is toxic to the environment and some of its associated biota. This study evaluated the growth pattern of Saccharomyces cerevisiae in cassava mill effluents. The Saccharomyces cerevisiae was isolated from palm wine following standard microbiological procedure. The Saccharomyces cerevisiae was inoculated into the sterile effluents and incubated for 15 days. At every 3days interval, 1ml of the effluents was obtained from the medium and the population density determined. Results of the growth showed that the population of Saccharomyces cerevisiae were 0.00 x 106 cfu/ml at day 0 (without inoculum), which rose to 2.88 x 106 cfu/ml at day 3, 272.67 x 106 cfu/ml at day 12 and decline slightly at day 15 (13.57 x 106 cfu/ml). There was significant variations (P<0.05) among the various period of study. The study showed that the growth of Saccharomyces cerevisiae in the effluent was optimum at day 12, then after the density began to decline.