Effect of post-treatment process of microalgal hydrolysate on bioethanol production

Abstract

Microalgae accumulate abundant lipids and are a promising source for biodiesel. However, carbohydrates account for 40% of microalgal biomass, an important consideration when using them for the economically feasible production of biodiesel. In this study, different acid hydrolysis and post-treatment processing of Chlorella sp. ABC-001 was performed, and the effect of these different hydrolysates on bioethanol yield by Saccharomyces cerevisiae KL17 was evaluated. For hydrolysis using H2SO4, the neutralization using Ca(OH)2 led to a higher yield (0.43 g ethanol/g sugars) than NaOH (0.27 g ethanol/g sugars). Application of electrodialysis to the H2SO4 + NaOH hydrolysate increased the yield to 0.35 g ethanol/g sugars, and K+ supplementation further enhanced the yield to 0.41 g ethanol/g sugars. Hydrolysis using HNO3 led to the generation of reactive species. Neutralization using only NaOH yielded 0.02 g ethanol/g sugars, and electrodialysis provided only a slight enhancement (0.06 g ethanol/g sugars). However, lowering the levels of reactive species further increased the yield to 0.25 g ethanol/g sugars, and K+ supplementation increased the yield to 0.35 g ethanol/g sugars. Overall, hydrolysis using H2SO4 + Ca(OH)2 provided the highest ethanol yield, and the yield was almost same as from conventional medium. This research emphasizes the importance of post-treatment processing that is modified for the species or strains used for bioethanol fermentation.

Algae: The Reservoir of Bioethanol

“…A high amount of ethanol production was noticed in dark fermentation. Seon et al [141] produced ethanol using different hydrolysis and post-treatment processes with Chlorella species ABC-001. Hydrolysis using H 2 SO 4 + Ca(OH) 2 and fermentation through Saccharomyces cerevisiae KL17 yielded augmented ethanol generation.…”

Comparative Study on the Various Hydrolysis and Fermentation Methods of Chlorella vulgaris Biomass for the Production of Bioethanol

“…Instead, they have to be firstly hydrolyzed either by using a chemical or enzymatic catalyst into monosaccharide (Vasić et al, 2021). Hydrolysis provides a significant contribution to biomass microalgae conversion into ethanol (Seon et al, 2020). This process also has a great potential to enhance glucose conversion (Sabiha-Hanim & Halim, 2018).…”

The ability of Pichia kudriavzevii to tolerate multiple stresses makes it promising for developing improved bioethanol production processes

“…have certain limitations including a reduced stress tolerance, leading to the risk of microbial contamination and decreased bioethanol yield (Robak and Balcerek 2018). As fermentation progresses, increasing ethanol and sodium chloride concentrations inhibit the viability and growth of yeast by creating osmotic shock or chemically reactive species (Zhang et al 2015;Saini et al 2018;Seon et al 2020). Previous studies have reported that Saccharomyces cerevisiae showed low tolerance to ethanol and osmotic stress during ethanol fermentation (Tekarslan-Sahin et al 2018;Arachchige et al 2019).…”

“…2018; Seon et al . 2020). Previous studies have reported that Saccharomyces cerevisiae showed low tolerance to ethanol and osmotic stress during ethanol fermentation (Tekarslan–Sahin et al 2018; Arachchige et al .…”