Bioethanol Production from Marine Macroalgae Waste: Optimisation of Thermal acid Hydrolysis

Abstract

Marine macroalgae waste, resulting from the accumulation of drifted algal biomass along the coastline, might be a relevant complementary raw material aiming sustainable bioethanol production. In the present study, the optimisation of thermal acid hydrolysis was performed using response surface methodology (RSM) considering the effect of three variables, namely, reaction time (10–60 min), acid concentration (0.1–2.5% (v/v) H2SO4) and biomass:acid ratio (5–15% (w/v)) on sugar concentration and yield. Under the best conditions, the resulting hydrolysates were fermented (7 days, 30 °C, 150 rpm, commercial yeast) to produce bioethanol. A statistically valid second-order model was obtained (r2 = 0.9876; Prob > F lower than 0.05), showing that sugar concentration is mostly influenced by the biomass:acid ratio while reaction time was not significant. The maximum predicted sugar concentration was 18.4 g/L, being obtained at 2.5% H2SO4 concentration and 15% (w/v) biomass:acid ratio, corresponding to a sugars yield of 12.5 g/100 g (less 36% than that obtained using 10% (w/v)). At the best conditions, the hydrolysates were fermented to obtain a bioethanol concentration up to 2.4 g/L and a 21 mgbioethanol/gbiomass yield, emphasizing the biomass potential for bioenergy production. Graphical Abstract

Improvement of Bacillus subtilis PI agarase production, hydrolysate scavenging capability assessment, and saccharification of algal biomass for green ethanol generation

“…Consequently, the creation of bioethanol from Carolina officinalis biomass was the second goal of our study. As our study indicated that the bioethanol production through fermentation process of 15% red algae yielded 8.22332 mg/ml which is equal to 27.4 mg bioethanol/ g biomass algae this is in contrast to Pardilhó et al 46 who reported that the bioethanol production using marine macoroalgae waste was 21 mg bioethanol / g biomass algae.…”