Ethanol production by S. cerevisiae was carried out using rice straw as substrate and B. subtilis and T. viride as hydrolyzing agents. The aim of this research is to compare the potential of rice straw (non-edible waste material) for bioethanol production using Bacillus subtilis and Trichoderma viride as cellulose hydrolyzing agents. The sample was dried and ground; and was subjected to chemical pretreatment and microbial hydrolysis to maximize sugar production. Standard methods were used to carry out isolation, identification and analysis of sample which includes proximate, mineral and physicochemical analysis. The sample was fermented for seven days during which ethanol yield was determined. Cellulose hydrolysis screening carried out on each of the two organisms revealed T. viride having the higher clearance zone of 1.8 cm, while B. subtilis had 1.5 cm. Proximate analysis obtained from the samples showed that the pretreatment method was relatively effective giving an increase in the cellulose and decrease in the hemicellulose and lignin contents of the samples. This showed rice straw having a cellulose content of 51.33 ± 0.17% after pretreatment. Potassium content was relatively high (17.96 mg/g), Hydrolysis using T. viride gave higher reducing sugar yield than that obtained using B. subtilis with 26.6 g and 12.21 g respectively. The pH was observed to decrease during fermentation while total titratable acidity observed showed an increase. Highest ethanol yield of 16.21 g/100 g was obtained using T. viride as hydrolyzing agent.
Lignocellulosic biomers have been found to possess great potential as substrates for various bioconversion processes; this is due to their vast availability coupled with their renewable nature. The direct conversion of lignocellulosic substrates is however hindered by their rigid and complex structural composition, which must be broken down via a process called pretreatment. This research aimed at comparing the effects of different methods used in pretreating lignocellulose. Samples of the selected biomers were subjected to various methods of pretreatments (mechanical, chemical, physicochemical and a combination method). Compositional analysis of each biomer was carried out before and after each pretreatment method, the pretreated biomers were then subjected to microbial hydrolysis using Trichoderma viride and Aspergillus niger for 5 days, after which estimation of reducing sugar present was carried out. Analytical contents of the samples showed high cellulose, hemicellulose and lignin contents (36.39, 26.52, 13.62 and 43.30, 32.30, 6.42% respectively). The combination of 2 or more methods proved more efficient than other individual methods, significantly increasing cellulose contents from 36.39% to 58.61% and 43.30% to 61.09% in wheat straw and corn stover respectively, while eliminating the lignin barrier from 13.62% to 3.82% and 6.42% to 2.38% respectively. The reducing sugar results proved that Trichoderma viride had the most sugar content of 0.55 g/g in corn stover after pretreatment with the combination method, making it more effective in cellulose hydrolysis.
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