Enhanced bio-ethanol production from Chlorella sp. biomass by hydrothermal pretreatment and enzymatic hydrolysis

Abstract Microalgae are considered a third generation feedstock for biofuel production. Apart from lipid accumulation, some microalgae also accumulate carbohydrates which could be extracted and used as substrate for other biofuels production. This research aimed to assess potential of biomass of microalgae, Chlorella sp., for its potential as a feedstock for ethanol production. Response surface analysis was used to determine the conditions for pretreatment of microalgae biomass by acid-hydrothermal. The analysis suggested the use of 20% biomass in 1.5% sulfuric acid at 117 °C for 20 min as suitable for the pretreatment as it resulted in the maximum ethanol of 5.62 ± 0.16 g/L, which was 3.5 times higher compared with using untreated biomass. Enhanced ethanol production was investigated by hydrolyzing the pretreated slurry with α-amylase and glucoamylase. Using glucoamylase alone was enough for hydrolyzing the slurry to improve ethanol production. By using 25 Unit/g algae of glucoamylase, ethanol produced from the hydrolysate increased to 10.58 ± 0.34 g/L or 52.88 ± 1.69 mg/g algae . Enhancing ethanol production from Chlorella sp. biomass by hydrolyzing the acid-hydrothermal pretreated slurry with glucoamylase resulted in a total of 7.1 times increase in ethanol production from Chlorella sp. biomass as compared with the use of the biomass without any treatment.