Vol.:(0123456789) 1 3 Bioprocess and Biosystems Engineering https://doi.org/10.1007/s00449-017-1881-0 RESEARCH PAPER Organic acid pretreatment of oil palm trunk: efect on enzymatic saccharifcation and ethanol production Kittipong Rattanaporn 1  · Prapakorn Tantayotai 2  · Theerawut Phusantisampan 3  · Peerapong Pornwongthong 4  · Malinee Sriariyanun 5 Received: 24 October 2017 / Accepted: 12 December 2017 © Springer-Verlag GmbH Germany, part of Springer Nature 2017 Abstract Efective lignocellulosic biomass saccharifcation is one of the crucial requirements of biofuel production via fermentation process. Organic acid pretreatments have been gained much interests as one of the high potential methods for promoting enzymatic saccharifcation of lignocellulosic materials due to their lower hazardous properties and lower production of inhibitory by-products of fermentation than typical chemical pretreatment methods. In this study, three organic acids, includ- ing acetic acid, oxalic acid, and citric acid, were examined for improvement of enzymatic saccharifcation and bioethanol production from oil palm trunk biomass. Based on response surface methodology, oxalic acid pretreated biomass released the maximum reducing sugar of 144 mg/g-pretreated biomass at the optimum condition, which was higher than untreated samples for 2.30 times. The released sugar yield of oil palm trunk also corresponded to the results of FT-IR analysis, which revealed the physical modifcation of cellulose and hemicellulose surface structures of pretreated biomass. Nevertheless, citric acid pretreatment is the most efcient pretreatment method to improve bioethanol fermentation of Saccharomyces cerevisiae TISTR 5606 at 1.94 times higher than untreated biomass. These results highlighted the selection of organic acid pretreatment as a potential method for biofuel production from oil palm trunk feedstocks. Keywords Organic acid pretreatment · Lignocellulosic biomass · Enzymatic saccharifcation · Bioethanol · Oil palm trunk Introduction Large-scale oil palm agriculture has been rapidly growing to promote cooking palm oil and biodiesel production. High production of such products and eradication and replacement of the old oil palm trees in every 20 years generate high amounts of oil palm wastes and residues. In 2013, it was estimated that 1.96 million tons of old oil palm trees, which could potentially generate 14,757 TJ of heat, were cut and uselessly burned in Thailand [1]. Disposal of the palm oil trees and residues by burning substantially releases green- house gases to the atmosphere and impairs air and environ- mental quality. Recently, many attempts have been drawn to recycle the oil palm wastes. Production of bioethanol by fermentation is an alternative way to sustainably use the waste and possibly secure the energy situation for Thailand. Oil palm trunk is lignocellulosic biomass consisting of cellulose, hemicellulose, and lignin. To make lignocellulosic biomass readily available for subsequent production of bio- fuels or value-added chemicals, the lignin–polysaccharide matrix must frst be broken down into simple fermentable sugars. However, lignocellulosic biomass has recalcitrant structures and chemical inhibitors that barricade hydrolysis and fermentations. Pretreatments are usually employed to disrupt the lignocellulose network and to modify the crystal- line structure of cellulose increasing cellulose availability and accessibility of hydrolytic enzymes [2]. Pretreatments * Malinee Sriariyanun macintous@gmail.com 1 Department of Biotechnology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand 2 Department of Microbiology, Faculty of Science, Srinakharinwirot University, Bangkok 10110, Thailand 3 Department of Biotechnology, Faculty of Applied Science, KMUTNB, Bangkok 10800, Thailand 4 Department of Agro-Industrial, Food and Environmental Technology, Faculty of Applied Science, KMUTNB, Bangkok 10800, Thailand 5 The Sirindhorn International Thai-German Graduate School of Engineering (TGGS), KMUTNB, Bangkok 10800, Thailand