Single and Combined Enzymatic Saccharification and Biohydrogen Production from Chlorella sp. Biomass
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Single and Combined Enzymatic Saccharification and Biohydrogen Production from Chlorella sp. Biomass Kawinda Sriyod 1,2,3 & Alissara Reungsang 2,3 & Pensri Plangklang 2,3 Received: 2 July 2020 / Accepted: 27 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The saccharification of Chlorella sp. biomass by single and combined commercial carbohydrase enzymes, Termamyl SC, Dextrozyme GA, and Cellic CTec2, was investigated. A substrate concentration of 100-g volatile solids (VS)/L was optimal for all the enzymes used. The optimal enzyme dosages for Termamyl SC, Dextrozyme GA, and Cellic CTec2 were 160-units/g VS, 320-units/g VS, and 40–filter paper units/g VS, respectively. The maximum reducing sugar yield, 130-mg/g VS, was obtained with a Dextrozyme GA treatment, which is equivalent to 38.37% hydrolysis efficiency based on carbohydrate content. A combinedenzyme treatment with Cellic CTec2, Termamyl SC, and Dextrozyme GA raised the reducing sugar yield and hydrolysis efficiency to 186.69-mg/g VS and 54.85%, respectively. Scanning and transmission electron microscopic images indicated morphological alterations in Chlorella sp. cells as an effect of enzyme treatment. Enzyme treatment improved the hydrogen production, hydrogen production rate, and hydrogen yield from Chlorella sp. biomass. The maximum hydrogen yield, 42.24-mL/g VSadded, was obtained from a Dextrozyme GA–hydrolyzed microalgae biomass. This was 82.46% higher than that obtained from untreated biomass (23.15-mL H2/g VSadded). Fourier-transform infrared analysis revealed that the functional groups of Chlorella sp. biomass, especially carbohydrates, were modified by both enzymatic treatment and the hydrogen fermentation process. This work demonstrated the efficient saccharification of Chlorella sp. biomass using combined cell wall– and starch-degrading enzymes. The results also elucidate that the pretreatment of Chlorella sp. biomass by commercial glucoamylase is a promising approach to solubilize internal starch granules and promote biohydrogen production without the addition of any cell wall–degrading enzyme. Keywords Microalgae . Biofuels . Dark fermentation . Enzyme pretreatment . FTIR analysis
Introduction Biohydrogen is an important alternative biofuel owing to its high specific energy (142 MJ/kg) [1] and clean combustion by-product, which is only water vapor [2]. Concern about
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12155-020-10191-y) contains supplementary material, which is available to authorized users. * Pensri Plangklang [email protected] 1
Graduate School, Khon Kaen University, Khon Kaen 40002, Thailand
2
Research Group for Development of Microbial Hydrogen Production Process from Biomass, Khon Kaen University, Khon Kaen 40002, Thailand
3
Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand
competition for food crops in energy production and problems arising from the severe pretreatment conditions nee
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