Bio-2,3-butanediol production from banana waste: Preliminary techno-economic evaluation of processing strategies

This study evaluates different fermentation strategies to produce 2,3-butanediol (2,3-BD) from banana industry waste, such as whole bananas (fruit + peels) and banana peels, selecting the most favorable from a technical and economic point of view. Both residues have enough free sugars (17.8 %–35.8 %), glucan (11.0 %–14.2 %) and hemicellulose (2.8 %–6.3 %), to be promising substrates for 2,3-BD fermentation. Saccharification was studied by comparing enzymatic hydrolysis, hydrothermal pretreatment, and hydrothermal pretreatment followed by enzymatic hydrolysis. Different fermentation scenarios were also compared regarding the 2,3-BD yield and productivity: Separate Hydrolysis and Fermentation (SHF), Simultaneous Saccharification and Fermentation (SSF), and direct fermentation without prior saccharification using Paenibacillus polymyxa DSM-365 as the fermenting microorganism. The results showed that the pretreatment step was not necessary to improve the release of fermentable sugars. Enzymatic hydrolysis was the most effective alternative for maximizing sugar recovery, reaching sugar concentrations of 18.1 g/L (recovery: 92.5 %) for banana peels and 33.3 g/L (recovery: ∼100 %) for whole bananas. The SSF strategy led to higher 2,3-BD concentrations of 15.0 g/L and 26.6 g/L for banana peels and whole bananas, respectively. The preliminary economic analysis indicated that SSF and direct fermentation could be the more cost-effective process alternatives for banana peels and whole bananas, respectively. Thus, it was demonstrated that banana waste is an interesting resource for the production of 2,3-BD. The bioprocess can be competitive when using a low-cost raw material and reducing the number of process steps compared to traditional technologies.