Bioethanol production from Ficus fruits (Ficus cunia) by Fusarium oxysporum through consolidated bioprocessing system

Abstract

Fusarium oxysporum is among the few filamentous fungi capable of fermenting ethanol directly from lignocellulose biomass (LCB). It has the essential enzymatic toolbox to disintegrate LCB to its monosaccharides, which subsequently fermented to ethanol under anaerobic and micro-aerobic conditions. However, the structural complexity of LCB and modest performances of wild fungi are major limitations for application in local biorefineries. This study assessed the potential of the locally isolated Fusarium oxysporum for the production of bioethanol from Ficus fruits (Ficus cunia) using Consolidated Bioprocessing (CBP). The maximum ethanol concentration achieved was at 5% substrate loadings with pH 6 irrespective of temperature variance, attaining a concentration of 3.54 g/L and 3.88 g/L at 28 °C and 32 °C, respectively. The monitoring of analytes (glucose, arabinose, cellobiose, xylose, acetic acid, ethanol, furfural, and HMF) in this study suggests the utilization of an array of sugars released from Ficus fruits, irrespective of the difference in the process parameters. This study also shows that CBP of freshly grounded Ficus fruits was feasible employing a mild hydrothermal pretreatment (autoclaved at 121 °C for 30 min in 1:10 w/v) and without supplementing any extraneous enzymes.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-022-03234-y.

Keywords: Consolidated bioprocessing: waste; Enzymes; Ethanol; Fusarium oxysporum.

Fig. 1

Ficus fruit (Ficus cunia) yield per fruiting phase during our study

Fig. 2

Ethanol production from fresh Ficus fruits (hydrothermally treated) and monitoring of analytes concentrations (acetic acid, arabinose, cellobiose, furfural, glucose, HMF, and xylose) during the course of fermentation at 5% (w/v) loadings at pH 4, pH 5 and pH 6 respectively by HG19 (Fusarium oxysporum strain), maintained at 28 °C. A–F represent one set of each experiment

Fig. 3

Ethanol production from fresh Ficus fruits (hydrothermally treated) and monitoring of analytes concentrations (acetic acid, arabinose, cellobiose, furfural, glucose, HMF, and xylose) during the course of fermentation at 5% (w/v) loadings at pH 4, pH 5 and pH 6 respectively by HG19 (Fusarium oxysporum strain), maintained at 32 °C. A–F represent one set of each experiment