One-step conversion of lemongrass leaves hydrolysate to biovanillin by phanerochaete chrysosporium atcc 24725 in batch culture

Abstract

One-step bioconversion of biovanillin using Phanerochaete chrysosporium ATCC 24725 with lemongrass leaves hydrolysates (LLH) was performed in batch culture. Initially, optimization of the lignocellulosic pretreatment practices using liquid hot-water with sodium bisulfite (0.5% w/v) towards the release of the ferulic acids was exhaustively investigated. The optimized results using central composite design recovered 0.750 ± 0.002 g/L of ferulic acid from the LLH. The bioconversion of biovanillin was grossly affected by the interactive effects of initial ferulic acid concentration, incubation temperature, incubation time and initial pH, and the biovanillin production was best determined at 0.5 g/L, 35 °C, 72 h, and 6 respectively. Bioconversion with the optimized condition revealed highest biovanillin production (93 ± 3 mg/L) with molar yield (23%) and acetic acid (12 ± 4 mg/L). Besides that, the use of the liquid hot water pretreatment approaches has clearly shows its effects on the respective untreated lemongrass leaves composition. Considerable alterations of the major lignocellulose contents were observed from the pretreated lemongrass leaves, which improved the cellulose content with 39%, but a decreased in the extractives, hemicellulose and lignin contents by 23, 29 and 46% were observed respectively. This proven the effectiveness of the pretreatment method in breaking the rigid structure of the lignocelluloses through increasing hemicellulose digestion, which instigates the disruption of lignin wall that resulted into the total loss of the lignocellulose structures. It further revealed that the lignin which serves as the shielding layer became fragmented and resulted to the cellulose exposure and accessible, thus eventually upsurges its contents. The design expert software ultimately revealed that all the optimization model terms were fit and significant statistically. Therefore, the one-step bioconversion using Phanerochaete chrysosporium ATCC 24725 with LLH as a source of ferulic acid epitomized a fabulous means of biovanillin production under the optimized conditions.