Comparative Analysis on Microwave and Pressure Cooker Pre-Treatment of Lignocellulosic Biomass in Glucose Production via Fungal Treatment

Oil Palm Empty Fruit Bunch (OPEFB) is lignocellulosic biomass waste generated from palm oil processing industries. Due to its significant compositions of cellulose, hemicellulose, and lignin, OPEFB can be further utilized and converted into value-added chemical products which can be used as alternative energy. Hence, the focus of this research is to analyze the effect of microwave pre-treatment (MP) and pressure cooker pre-treatment (PCP) parameters on OPEFB lignin reduction. The treated OPEFB was directly processed using two serial fungal treatment processes. The first fungal treatment process (FT-1) was to maximize the OPEFB lignin removal while the second fungal treatment process (FT-2) was to maximize the glucose production. Combination of microbes such as Phanerochaete chrysosporium, Trichoderma harzianum, Aspergillus niger, and Tricodherma viride was used for both fungal treatment processes. The OPEFB passing 25-mesh screening was used as raw materials. The raw materials mixed with 0.05 w/w NaOH pellets and water to achieve a concentration ratio of 3/50 (w/v) were pre-treated with either MP or PCP. Subsequently, the slurry produced from the pre-treatment process was introduced to FT-1 (P. chrysosporium for 5 days) and finally to FT-2 (T. harzianum, A. niger and T. viride for 4 days). The compositions of lignin, cellulose, hemicellulose, and glucose were analyzed at each process transition and the end of the whole process. It was observed that PCP (60 mins) was the best pretreatment process with 39.23%-w of lignin removed. On the other hand, combination of MP (150 watts, 60 mins) was followed with FT-1 removed 66.67%-w of lignin. Only around 38.37%-w of lignin was removed when using the whole process, e.g., MP (150 watts, 60 mins), FT-1, and FT-2. The highest composition of glucose, ca. 131.02%-w, was obtained when 40-min PCP followed with FT-1 and FT-2 was applied. The obtained results exhibited that large lignin removal did not necessarily promote high glucose yield in the final product as observed in the 60-min PCP, e.g., P. chrysosporium consumed not only lignin but also presumably hemicellulose and cellulose.