Evaluation of different pretreatment methods on bioconversion of wheat straw and corn strover

Abstract

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.