High-Energy Ball Milling as a novel method to mecanolyze raw material for bio-H2 production by dark fermentations of Escherichia coli

Abstract

This study analyzed the use of high-energy ball milling as a new raw material treatment for biohydrogen (Bio-H2) production by dark fermentation of Escherichia coli. Potato (Solanum tuberosum) and Taro (Colocasia esculenta), fresh and dry, were used as raw materials. A colorimetric method was used to quantify the fermentable sugar content of the raw materials. The bacterial growth kinetics, Bio-H2 production, pH, and Oxide-Reduction Potential (ORP) were monitored during dark fermentation. The formation of secondary metabolites was monitored by 1H NMR through the fermentation. Glucose was used as a control. Mechanolysis increased the fermentable sugar content of dry and fresh potatoes by 5 and 2 times, respectively, while the fermentable sugar content of dry and fresh Taro increased by 13 and 2 times, respectively. The Bio-H2 yields in dry and fresh potato were 32.6 and 34.4 cm3/g RS, while in dry and fresh Taro were 37.0 and 58.8 cm3/g RS. However, the better Bio-H2 yield per g of raw material was dry Taro (7.7 cm3/g Rm). Fresh Taro reaches a Bio-H2 production efficiency of 59.4 % with respect to glucose. The highest biomass growth was also observed in fresh Taro. In addition, the metabolic pathways of the fermentation process for producing Bio-H2 by E. coli from raw materials modified by HEBM are proposed.