Granular starch hydrolysis of babassu agroindustrial residue: A bioprocess within the context of biorefinery

The conversion of renewable feedstocks into a range of commercial products and energy is the principle underlying the concept of biorefinery. In this work, two agroindustrial by-products from babassu were used as unconventional biomasses to develop a sustainable process. Babassu cake was used to produce a multienzyme complex, which was able to hydrolyse starch granules and to release free amino nitrogen from babassu flour, yielding a hydrolysate rich in carbon and nitrogen nutrients. To exemplify its possible applications, different strategies for ethanol production by simultaneous saccharification and fermentation (SSF) were investigated and that comprising a 4-h hydrolysis step at 50 °C followed by 44 h of SSF at 32 °C showed the most promising results (53.6 g/L ethanol, 83% efficiency of starch into ethanol and productivity of 1.12 g/(L h)). On-site enzymes promoted better results than a commercial enzyme product (110.9 ± 6.6 g/L versus 74.5 ± 1.8 g/L glucose releases, respectively), and showed high efficiency and productivity also on corn flour, either similar or superior to those reported for the industrial-scale dry-grind process.