Screening of Ligninolytic Fungi and Optimization of Pretreatment Process for Bioethanol Production from Empty Palm Oil Bunches (OPEFB)

Abstract

Abstract The high fuel demand causes depletion of non-renewable energy. Fuel substitution such as bioethanol need to be discuss as an alternative to gasoline. Second-generation bioethanol utilizes lignocellulosic biomass. Empty Palm Oil Bunches (OPEFB) is one of the abundant sources of lignocellulosic biomass in Indonesia, that can be potentially converted into bioethanol. This study was conducted to determine the most effective fungal pretreatment on lignin and cellulose content, and measuring enzyme activity. Optimization of temperature, pH, and substrate concentration were carried out using RSM. Trametes versicolor, Pycnoporus cinnabarinus (white-rot fungi), and Aspergillus niger, Aspergillus terreus, Trichoderma harzianum, Trichoderma viride (brown rot and soft rot fungi) were examined in this study. Fungal pretreatment was conduted by adding the fungal suspension to OPEFB, then incubated at 28°C for 14 days. This showed that A. niger had the highest ability to degrade lignin (7.58 ± 1,5%) and increase cellulose (33.56%). The highest laccase and MnP activities were produced by P. cinnabarinus (9,26 and 123.81 U/ml). The highest LiP activity was produced by A.niger (3276,8 U/ml). XRD analysis resulting in reducing CCI in pretreated sampel. Optimization of pretreatment using A.niger which produce highest lignin removal obtained at 30 oC, pH 5, and 7 grams OPEFB (14.21 ± 0.50%). At 25 oC, the highest cellulose content was obtained (53.08%). The pretreated sample using A. niger was hydrolyzed with enzymes, resulting in 1.09 g (36.30%) of reducing sugar at 48 hours at 50 oC, by DNS method. Saccharomyces cerevisiae were used for fermentation, resulting in ethanol of 0.56%.