Oil palm fiber biodegradation: physico-chemical and structural relationships

MAIN CONCLUSION: X-ray microtomography results revealed that delignification process damaged the oil palm fibers, which correlated well with reduction of lignin components and increase of the phenolic content. Biodegradation investigation of natural fibers normally focuses on physico-chemical analysis, with less emphasis on physical aspect like fiber structures affect from microbial activity. In this work, the performance of Pycnoporus sanguineus to delignify oil palm empty fruit bunch fibers through solid-state fermentation utilizing various ratio of POME sludge was reported. In addition to tensile testing, physico-chemical and X-ray microtomography (µ-CT) analyses on the oil palm fibers were conducted to determine the effectiveness of the degradation process. The best ratio of fiber to fungi (60:40) was chosen based on the highest lignin loss and total phenolic content values and further investigation was performed to obtain fermentation kinetics data of both laccase and manganese peroxidase. µ-CT results revealed that delignification process damaged the pre-treated and untreated fibers structure, as evident from volume reduction after degradation process. This is correlated with reduction of lignin component and increase of the phenolic content, as well as lower stress-strain curves of the pre-treated fibers compared to the untreated ones (from tensile testing). It is suggested that P. sanguineus preferred to consume the outer layer of the fiber, before it penetrates through the cellular structure of the inner fiber.