Butanol Production from Leftover Beverages and Sport Drinks

The aim of this paper is twofold: i) to identify an alternative disposal process for the industry of high sugar content beverages (HSCBs); ii) to contribute to the study of butanol production by Clostridium acetobutylicum using no-edible feedstock. HSCBs were used as a renewable feedstock to produce butanol by C. 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 1000 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 both on the sugars and the HSCBs supplemented with no-carbon nutrients. 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 (rBMAX) was estimated for each sugar at the onset of the solventogenesis: once set the sugar concentration, the rBMAX 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 hydrolysed. Under optimized conditions the butanol concentration and yield were: pineapple-juice) 13.3g/L, 0.16g/g; pear-juice) 12.8g/L, 0.14g/g; lemon syrup) 13.2g/L, 0.19g/g; almond-syrup) 13.8g/L, 0.14g/g; commercial soft drinks) 13-14g/L, 0.17-0.18g/g; sport dink) 5.9g/L, 0.11g/g. The maximum butanol production rate was 0.12g/(L h), obtained with the sport drink.