Total Sago Effluent Concentrate (TSEC) for Bioethanol Production via Fed- Batch Simultaneous Saccharification and Fermentation (SSF)
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UNIVERSITI MALAYSIA SARAWAK
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The extraction of sago in sago processing industries requires substantial volumes of water, which subsequently generates large quantities of sago residue. This waste is often discharged into nearby streams, contributing to environmental pollution. Sago processing waste stream, or sago effluent, comprises a mixture of wet solid biomass and liquid hydrolysate. This industrial waste is rich in carbohydrates, particularly lignocellulosic materials, making it a potential feedstock for bioethanol production. In this study, the sago effluent was pretreated physically using mechanical pulverisation and centrifugation to produce a starch-rich wet biomass referred to as Total Sago Effluent Concentrate (TSEC). The TSEC was then utilised as a feedstock for bioethanol production in addition to enhance the utilisation of lignocellulosic materials from sago residue as well as to minimise unethical disposal of valuable resources. Compositional analyses were conducted on the TSEC prior to the enzymatic saccharification and fermentation process. Starch and fibre analyses were conducted using the Phenol-sulfuric Acid (PSA) assay, Acid Detergent Fibre (ADF), Neutral Detergent Fibre (NDF), Klason Lignin determination and standard protocol for ash content. Based on the results, TSEC comprised of 88.11 ± 2.09% sago effluent hydrolysate and 3.56 ± 0.80% sago hampas. The TSEC was subjected to further compositional analyses whereby 1.31 ± 0.05% of free starch was found in the sago effluent hydrolysate whilst, solid component was consisted of 65.87 ± 4.25% starch, 5.95 ± 1.53% cellulose, 18.20 ± 1.60% hemicellulose, 5.25 ± 0.70% lignin and 0.58 ± 0.40% ash. These compositional values suggest that the TSEC is a desirable feedstock for bioethanol production via fed-batch simultaneous saccharification and fermentation (SSF) catalysed by amylolytic enzymes (α-amylase and glucoamylase) and fermenting yeast, Saccharomyces cerevisiae. The SSF studies were conducted via fed-batch fermentation in iv both non-buffered and buffered broth with varying strengths (25 mM, 50 mM and 100 mM) of citrate buffer at different biomass concentrations. Results indicated that SSF on TSEC yielded maximum ethanol concentration of 23.44 ± 4.16 g/L with the Theoretical Ethanol Yield (TEY) of 62.94 ± 11.18% in the non-buffered broth. There was no significant difference in ethanol produced in the different buffered broths. The highest ethanol concentration detected in 25 mM was 23.22 ±2.44 g/L or 62.33 ± 6.57% TEY, followed by 55.33 ± 4.80% TEY (20.67± 2.85 g/L) in 50 mM. The highest ethanol yield detected in the sample buffered by 100 mM citrate buffer was at 20.61 ± 1.79 g/L with equivalent TEY of 55.33 ± 4.82%. This study concludes that TSEC is viable feedstock for bioethanol production via the fed-batch SSF process in a non-buffered fermentation system.