Wheat straw degradation and production of alternative substrates for nitrogenase of Rhodobacter sphaeroides

Cellulose is a major component of plant biomass and could be applied in the production of biofuels, especially bioethanol. An alternative approach is production of a clean fuel - hydrogen from cellulosic biomass. In this paper an innovatory model of cellulosic waste degradation has been proposed to verify the possibility of utilization of cellulose derivatives by purple non-sulfur bacteria. The concept is based on a two-step process of wheat straw conversion by bacteria in order to obtain an organic acid mixture. In the next stage such products are consumed by Rhodobacter sphaeroides, the known producer of hydrogen. It has been documented that Cellulomonas uda expresses cellulolytic activity in the presence of wheat straw as an only source of carbon. R. sphaeroides applied in this research can effectively consume organic acids released from straw by C. uda and Lactobacillus rhamnosus and is able to grow in the presence of these substrates. Additionally, an increased nitrogenase activity of R. sphaeroides has been indicated when bacteria were cultivated in the presence of cellulose derivatives which suggests that hydrogen production occurs.