Coupled Production of Fatty Acid Alkyl Esters as Biodiesel and Fermentative Xylitol from Indian Palm (Elaeis guineensis Jacq.) Kernal Oil in a Biorefinery Loom

Palm kernel oil (PKO) is a non-edible oil which is enriched with saturated fatty acids that can be used as a raw material for many industrial applications. Indian PKO (IPKO) was chosen in this study which has been explored sporadically in industries. IPKO was characterized and utilized for the synthesis of fatty acid alkyl esters through transesterification (solvolysis) using methanol and ethanol solvents coupled with alkali catalysts such as sodium hydroxide (NaOH) and potassium hydroxide (KOH). Upon comparison, methanol and NaOH resulted in the maximum biodiesel (esters) yield of 67.77% as compared to ethanol-based solvolysis. Compositional analysis of fatty acid methyl esters (FAMEs) through GC-MS elucidated the presence of long chain (C12:0 to C18:1) esters, which can be utilized as biodiesel. Therefore, IPKO FAME has been tested as diesel blend in engines without any modification, where, B5 (5% v/v) blend showed at-par fuel characteristics and engine efficiency as compared to non-blended diesel with minimal emissions. To induct a waste circular reprocessing startegy, crude glycerol resulted from transesterification of IPKO was supplemented to Candida tropicalis NCIM3118 for xylitol (a sweetener) synthesis. The results indicated that upon supplemention of IPKO crude glycerol as co-substrate, enhancement in xylitol production of about 0.93 g(xylitol)/g(total organic carbon) as compared to only xylose as 'C' source (0.81 g(xylitol)/g(total organic carbon)) was observed with efficiency improvement in overall growth kinetic behavior. This study demonstrates the circular economy approach in which that the IPKO can be utilized for biodiesel production, while, the by-product (crude glycerol) generated could be deployed for xylitol production.