Production of Liquid Biofuel from Fresh Sago Effluent

Huang, Chai Hung (2018) Production of Liquid Biofuel from Fresh Sago Effluent. Masters thesis, Universiti Malaysia Sarawak(UNIMAS).

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Abstract

Sago starch processing factories are generally located nearby waterways, where wastewater is normally discharged, resulting in environmental issues. Sago effluent comprises mainly of macromolecules in the form of polysaccharides that can potentially be exploited to produce bioethanol. Hence, in this study, sago effluent and its constituents were used for bioethanol production in addition to recover the energy lost in the waste stream as well as purifying the effluent. Prior to the enzymatic saccharification and fermentation process, the sago effluent was subjected to starch and fibre analysis using phenol-sulphuric acid assay, Acid Detergent Fibre (ADF), Neutral Detergent Fibre (NDF) and Klason lignin determination as well as determination of ash content using standard protocol. Based on the result of compositional analysis, total sago effluent (TSE) used was comprised 97.00 ± 0.02% sago effluent hydrolysate and 3.00 ± 0.02% sago hampas. After further compositional analyse, the sago effluent hydrolysate was found to be consisting of 2.00 ± 0.02% total carbohydrate, while sago hampas was composed of 55.40 ± 0.02% starch, 23.64 ± 0.77% cellulose, 9.07 ± 1.18% hemicellulose, 4.01 ± 0.51% lignin, and 2.23 ± 0.01% ash. The initial stage of the study was utilised sago effluent hydrolysate for bioethanol production via simultaneous saccharification and fermentation (SSF) with the aid of amylolytic enzymes and the yeast Saccharomyces cerevisiae. Results indicated that sago effluent hydrolysate was efficient in generating high ethanol yield at 8.39 ± 0.20 g/l (84.89 ± 4.56% Theoretical Ethanol Yield; TEY) as its production was insignificant different compared to commercial starch loading (8.88 ± 0.07 g/l or 91.49 ± 0.74% TEY). Next, SSF was conducted on sago hampas at 2.5%, 5.0% and 7.5% (w/v) feedstock loadings for 5-day with aid of amylolytic enzymes, commercial cellulase and fermentative synthesis of ethanol of S. cerevisiae, to establish the optimum feedstock loading for ethanol production. The highest ethanol production was detected in 5.0% (w/v) sago hampas at 17.79 ± 0.17 g/l or 79.65 ± 0.78% TEY at 48 h. This was significantly higher than ethanol productions in the broth with 2.5% and 7.5% (w/v) sago hampas loadings, which were 8.38 ± 0.07 g/l (75.00 ± 0.63% TEY) and 23.28 ± 0.61 g/l (69.48 ± 1.81% TEY) respectively. However, by corresponding to TEY, 7.5% (w/v) sago hampas loading was shown lowest ethanol production due to the inhibition of high carbohydrate content on cellulase activities. The final study in this research the optimisation of the simultaneous saccharification and bioethanol fermentation process, termed as sequential saccharification and simultaneous fermentation (SSSF). SSSF was conducted on TSE by involving amylolytic stage and cellulolytic stage in order to minimise the inhibition of high sugar content on cellulase activities. High carbohydrate and glucose concentrations were detected at 0 h, indicating the carbohydrate-rich of TSE and the initial saccharification of starch by amylases added at 50 °C. Additionally, occurrence of glucose extinction was due to the efficient conversion by the yeast. Meanwhile, the slightly increased of total carbohydrate was marking the starting of cellulolytic stage. The highest ethanol production was peaked at 20.01 ± 0.73 g/l, corresponding to 86.56 ± 3.17% TEY at 48 h. At the end of fermentation period, 3.50 ± 0.20 g/l of residual carbohydrates was detected as there was no utilisation of xylose and arabinose by the yeast. As a conclusion, sago effluent and its onstituents were found to be potentially excellent feedstocks for bioethanol production via saccharification and fermentation process.

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