Potentials of sago fibre hydrolysate (SFH) as a sole fermentation media for bioethanol production

Abstract

Sago wastewater which contains starchy fibres from sago starch processing mills is commonly discharged directly to nearby stream thus contribute to serious environmental pollution. Sago fibre which is known to be a local agricultural waste mainly contains residual starch of about (50 – 60 %) together with cellulosic component. These contribute to high carbohydrate contents which suitable to be used as substrate for ethanol production. Initially, sago fibre (SF) was converted into sago fibre hydrolysate (SFH) via enzymatic hydrolysis using commercial enzymes; Liquozyme SC DS and Spirizyme Fuel HS. This study emphasized on batch ethanol fermentation by commercial baker’s yeast utilizing 50 g/L and 80 g/L glucose of SFH as the sole fermentation medium. The results indicate that 50 g/L glucose from SFH media is capable of generating maximum ethanol concentration at 20.33 ± 0.15 g/L, with highest glucose consumption efficiency (97.78 %) during 24 hours of fermentation. Similar concentration of bioethanol was obtained in 50 g/L glucose of commercial glucose (CG) media which is at 20.04 ± 0.06 g/L. However, lower ethanol concentration was obtained in both 80 g/L glucose from SFH (13.32 ± 0.12 g/L) and CG (12.98 ± 0. 04 g/L media), respectively. Addition of yeast extract at 3 g/L into 80 g/L SFH as well as CG significantly improve ethanol fermentability (SFH: 41.04 ± 0.04 g/L and CG: 33.96 ± 0.04 g/L). Based on statistical analyses, 50 g/L glucose of SFH media exhibit the highest ethanol yield (0.42 ± 0.003 g/g) and highest fermentation efficiency (81.35 ± 0.572 %) compared to 80 g/L glucose (0.24 ± 0.008 g/g; 46.65 ± 1.50 %). Conclusively, this study demonstrated that glucose in SFH was metabolized efficiently by commercial baker’s yeast during ethanol fermentation, thus suggesting the capability of SFH to be a feasible and alternative substrate with less expensive nitrogen source for the renewable bioethanol production.

Potential of Candida glabrata from ragi as a bioethanol producer using selected carbohydrate substrates

“…The interest in producing renewable fuels has increased tremendously over recent years due to the instabilities of fossil fuel supplies and increasing global demands (Wei et al 2015;Wong and Vincent 2019;Mohammad et al 2020). Alternative liquid biofuel, such as bioethanol, is seen as the current choice of such renewable fuel to supplement and substitute petroleum-based fuel, due to its sustainability and carbon dioxide neutrality (Vincent et al 2015;.…”

“…It is one of the main cost factors for the ethanol industry (Vincent et al 2015). There are currently many feedstock sources that are used as substrates for bioethanol production (Techaparin et al 2017;Ahorsu et al 2018;Mohammad et al 2020). When substrates such as lignocellulosic biomass are used to produce bioethanol, this type of bioethanol is termed as second-generation bioethanol (Zhang et al 2016).…”

“…The desired microorganism should be robust and capable of converting substrates to ethanol effectively. The most common examples of ethanol producers are Saccharomyces cerevisiae, Zymomonas mobilis and Fusarium oxysporum (Ali et al 2016;Vincent et al 2018;Mohammad et al 2020). Among these, S. cerevisiae has been mostly used in alcoholic fermentation due to its ethanol productivity.…”

“…According to Vincent et al (2020), about 7 tons of TSE is discharged into the rivers per day from typical sago starch factories. This waste needs to be handled properly to avoid water pollution (Mohammad et al 2020). TSE consists of sago hydrolysate, which is the liquid part while the solid component is called sago hampas.…”

Enhancement of very high gravity bioethanol production via fed-batch fermentation using sago hampas as a substrate

“…Sago hampas on a dry basis has 58% starch apart from other lignocellulosic components (Linggang et al, 2012). Our previous works have highlighted the feasibility of using sago hampas as a substrate for bioethanol production (Awang-Adeni et al, 2013;Mohammad et al, 2020). The remaining challenge in using sago hampas as a feedstock for bioethanol production, however, lies in the technique used to enhance the productivity of bioethanol fermentation.…”