Bioconversion of lignocellulosic palm byproducts into enzymes and lipid by newly isolated oleaginous fungi

• Cellulolytic oleaginous fungi could directly convert lignocellulosic biomass into lipid.
• The fungal lipid has potential to be used as biodiesel feedstock.
• Alkaline pretreatment of the substrate enhanced enzymes production by the fungi.
• Response surface methodology successfully optimized the conditions for solid state fermentation.

Direct conversion of palm pressed fiber (PPF) and palm empty fruit bunches (EFB) into enzymes and lipid by oleaginous fungi were performed through solid-state fermentation (SSF). Among the strains tested, TSIP9 converted PPF and EFB into lipid with the highest yield of 31.1 ± 1.7 mg/gram dry substrate (gds) and 37.5 ± 2.2 mg/gds, respectively. It also produced high activity of cellulolytic enzymes. It was identified as Aspergillus tubingensis. The similar fatty acids of its lipid to those of plant oil indicate its suitable use as biodiesel feedstock. The cellulase and xylanase production by this strain was improved when EFB was pretreated with alkaline. When alkaline-pretreated EFB was added with palm kernel cake (PK) as an alternative nitrogen source and the culture conditions were optimized through response surface methodology (RSM), the production of lipid, cellulase and xylanase were increased up to 88.5 ± 4.9 mg/gds, 26.1 ± 0.1 U/gds and 59.3 ± 0.3 U/gds, respectively. This study reveals the potential use of in situ cellulolytic enzymes producing fungi and the optimal conditions for direct conversion of lignocellulosic biomass into lipid.

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