Pretreatment and process optimization of spent seaweed biomass (SSB) for bioethanol production using yeast (Saccharomyces cerevisiae)

The study aimed to utilize the industrial spent seaweed biomass (SSB) for effective ethanol production using yeast as a fermenting microorganism. Pretreatment of SSB was optimized using different acids. The highest percentage of spent biomass was obtained from G. corticata (12.53 ± 2.66% DW). The proximate, ultimate and biochemical constituents of spent biomass were calculated. The total sugar (440 ± 40 mg/g DW), reducing sugar (129.85 ± 10.23 mg/g DW) and protein (11.08 ± 0.11 mg/g DW) content of SSB were analysed. Pretreatment was optimized using three different acids. The effect of different pH (4.5, 5.0, 5.5 and 6.0) and temperature (30 and 35 °C) on ethanol production using baker’s and MTCC yeast was studied. At 35 °C, the maximum (4.85% w/w) ethanol production was achieved in a fermentation process maintained at pH 4.5 and 5.0 at 24 h and 72 h, respectively. Substrate fermented with MTCC yeast recorded the maximum production of ethanol (4.98% w/w) at pH 4.5 within 48 h. The fermentation process was scaled up to 300 mL for ethanol production, and achieved 3.75% w/w ethanol (72 h, pH 5.5). To conclude, in future SSB would be a potential renewable novel substrate for bioethanol production when compared to other lignocellulosic substrates.