Butanol Production from Leftover Beverages and Sport Drinks

The aim of this paper is twofold: (1) to identify an alternative disposal process for the industry of high-sugar-content beverages (HSCBs) and (2) to contribute to the study of butanol production from non-edible feedstocks. HSCBs were used as a renewable feedstock to produce butanol by Clostridium acetobutylicum DSM 792. Four types of commercial beverages were investigated: fruit juices (pineapple and pear), syrups (lemon and almond), soft drinks, and a sport drink. They contained high levels of sugar—between 50 and 1,000 g/L—mainly glucose, fructose, and sucrose. These sugars were also tested individually and in a mixture. The batch fermentation tests were characterized in terms of metabolite and cell production, and sugar conversion. C. acetobutylicum was able to grow on HSCBs supplemented with yeast extract and minerals. The tests on the sugars (alone or mixed) highlighted the predisposition of C. acetobutylicum to metabolize them and to produce butanol. The production rate of butanol (r_B ^MAX) increased in the following order: glucose, fructose, and sucrose. The HSCB pre-hydrolysis improved the fermentation performance in terms of solvent production and sugar conversion (almost 100 %) because sucrose has been hydrolyzed. Under optimized conditions the butanol concentration and yield were—13.3 g/L, 0.16 g/g for pineapple juice; 12.8 g/L, 0.14 g/g for pear juice; 13.2 g/L, 0.19 g/g for lemon syrup; 13.8 g/L, 0.14 g/g for almond syrup; 13–14 g/L, 0.17–0.18 g/g for commercial soft drinks, and 5.9 g/L, 0.11 g/g for sport drinks. Among the beverages tested, the sport drinks gave the maximum butanol production rate of 12 g/L h.