Hydrogen production by hyperthermophilic bacterium Thermotoga neapolitana from food industry waste

Since hydrogen is a clean, high energy content and low emission fuel, sustainable hydrogen production from renewable resources is a topic of great interest. In particular, fermentative production of hydrogen has recently received considerable attention thanks to its possible implementation in cost-effective processes [1]. Thermotoga neapolitana, a member of the hyperthermophilic order of eubacteria Thermotogales, is considered an ideal organism for H2 production because of the low oxygensensitive hydrogenases and the thermophilic character of growth of this microorganism. Indeed, hydrogen bio-production from carbohydrates is thermodynamically favorable at high growth temperatures [1,2]. Since bio-hydrogen production by T. neapolitana has been mainly carried out on rich media [3,4], the aim of this study is to investigate the feasibility of a cost-effective process of hydrogen production from food industry wastes such as molasses and whey. We initially conducted batch cultures of T. neapolitana grown on rich defined media ATCC 1977 with glucose as carbon source [5]. The optimal concentration of glucose for hydrogen production was 7.5 g/l, in agreement with literature data [6]. On the basis of preliminary data, the yield of conversion of glucose into hydrogen seems to be close to the theoretical maximum, equal to 4 mol H2 / mol glucose. We observed a significant production of acetate, whereas butyrate was not detected. Subsequently, we carried out experiments by using T. neapolitana cultures grown on rich defined media ATCC 1977 with molasses as carbon source. The H2 production yields were similar to those obtained with glucose. Further experiments will evaluate the H2 production by T. neapolitana cells grown on minimal medium supplemented with either molasses or whey as only carbon sources. Finally, the ability of T. neapolitana to form a stable biofilm on different kind of supports in rich and defined media is presently under investigation in order to analyze physiological and metabolic features of T. naepolitana under biofilm and planktonic growth conditions, and to evaluate the feasibility of an attached-growth process of hydrogen production, so as to minimize the risk of biomass washout.