Optimization of the bio-hydrogen production by aphototrophic bacterium

Background and Aim : Nowadays one of the biggest concerns around the world is providing ofsufficient amounts of energy, needed by countries, continuously. Despite the limitation of fossilresources, the information shows the doubling of global energy demand in the recent last decade.So looking for new sources of energy that are renewable and affordable is one of the importantapproach of researchers. Bio-hydrogen is the best green foul for this purpose.Methods : In this research, three of the most important factors affecting the amount of biologicalhydrogen gas produced by Rhodobacter spheroeides, include the type of precursor (includingsugarcane molasses, non-alcoholic beverage industry waste, and dairy industry waste), lightintensity (۲۳۰۰, ۳۳۰۰, and ۵۳۰۰ lux) and initial pH (۷, ۸, and ۹) were examined. The ANOVAanalysis was done to select the best level of each factor. In order to examine the precursors moreprecisely, the physicochemical characteristics of the precursors (sugar, lipid, and protein content)were analyzed.Results : According to the results, sugarcane molasses precursor with biological hydrogenproduction of ۵۷۱.۳۸ ml/l (in ۴ days) medium had the highest amount of hydrogen among thestudied precursors. It can be related to the type of nutrients in this substrate. Based on thecharacterization results of three substrates, beverage waste had the highest protein andcarbohydrate content and molass had the highest fat content. Also, the light intensity of ۵۳۰۰ luxwith a value of ۷۲۷.۹۹ ml/l medium (in ۴ days) had the best result for biofuel production. It is dueto increased stimulation of phototrophic systems. About the initial pH of the culture medium, itwas shown that the initial pH of ۹ with the production of ۸۹۵.۸۴ ml/l medium (in ۴ days) was theoptimum pH.Conclusion : It can be attributed to increased tolerance to the accumulation of toxic cellularmetabolites such as volatile fatty acids. Finally, this rate of biohydrogen production with aninexpensive substrate in such a short time is very important achievement in the energy field.

کلیدواژه ها:

Rhodobacter spheroeides ، molasses ، beverage ، dairy ، energy.