Biological pretreatment of oil palm empty fruit bunch by a local isolate of Schizophyllum commune ENN1 for production of fermentable sugars

Oil palm industry in Malaysia plays a major role in national socio-economic development. In line with the expansion of the industry, oil palm biomass is generated abundantly from the plantations and mills. Oil palm empty fruit bunch (OPEFB) is the most abundant lignocellulosic biomass generated from palm oil mill, composed of 25-44% cellulose, 25-28% hemicellulose and 19- 27% lignin. The cellulose and hemicellulose components can be converted into fermentable sugars after being pretreated by either physical, chemical, physicochemical, biological or combination of these pretreatment methods. Currently, physicochemical pretreatment is the most common pretreatment method used to pretreat and convert OPEFB into fermentable sugars. However, this type of pretreatment utilised chemicals that lead to environmental issues and high operational cost. Therefore, biological pretreatment by fungi has been considered as an alternative to pretreat OPEFB as it is environmental friendly and requires low cost for the process. The first objective in this study was to evaluate the feasibility of Schizophyllum commune ENN1 in removing lignin of OPEFB through biological pretreatment. The second objective is to investigate the significant parameters affecting the biological pretreatment of OPEFB by S. commune ENN1 for fermentable sugars production through one-factor-at-a-time (OFAT) method. The biological pretreatment by locally isolated fungus identified as Schizophyllum commune ENN1 was conducted using unwashed OPEFB without supplemented with nutrients or any moistening agents. The lignocellulosic compositional analysis showed that 53.8% of lignin was removed after biological pretreatment using S. commune ENN1 compared to 38.6% of lignin removal using P. chrysosporium UIA. The determination of residual oil content showed that S. commune ENN1 was able to reduce the residual oil content by 85.3% while maintaining the moisture content in the range of 51-40%. The effect of incubation time (7-28 days), temperature (25- 40°C) and amount of substrate (3-9 g) were analysed in the biological pretreatment. The results also showed the highest lignin removal of 55.2% after 14 days of incubation time. This is followed with significant lignin removal by 66% at temperature 30°C. Meanwhile, the amount of substrate at 5 g gives the highest lignin removal by 71.7%. A maximum lignin removal of 67.9% was achieved at optimum conditions using 5 g of substrate after 14 days of incubation time at temperature 30°C. The highest amount of reducing sugars obtained from biological pretreatment using S. commune ENN1 was 230.4 ± 0.19 mg/g with 54% of hydrolysis yield in 96 h. This amount is 1.8-fold the amount obtained from untreated OPEFB (128.2 ± 0.00 mg/g) with the hydrolysis yield of 35.17%. The finding from this study showed that S. commune ENN1 was feasible to remove the lignin of OPEFB through biological pretreatment for fermentable sugars production.

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