Influence of laser photoactivated graphitic carbon nitride nanosheets and nickel nanoparticles on purple non-sulfur bacteria for biohydrogen production from biomass

Abstract

The objective of this study is to increase biohydrogen production from biomass using laser photoactivated nanomaterials. Light saturation of photo-fermentation is a vital factor that influences fermentation effectiveness and hydrogen yield. In this study, it is hypothesized that the bio-stimulation of hydrogen-producing purple non-sulfur (PNS) bacteria using laser photoactivated nanomaterials can enhance the endurance ability of such bacteria to unsteady light irradiation, where this leads to overcome the challenge of light saturation. Furthermore, the addition of nanomaterials leads to bio-stimulate the bacterial cells and enhance their activity and growth rate and, therefore, increase biohydrogen production from biomass. A biohydrogen production system and a model of photobioreactor were manufactured and installed. Food wastes were collected from kitchen leftovers of different fast-food suppliers and were used in this study as feedstocks for biohydrogen production. The production process was conducted as following: exposing 16.5 mg/l of graphitic carbon nitride nanosheets on the one hand and 50 mg/l of nickel nanoparticles on the other hand to a helium-neon green laser radiation source with a wavelength of 543 nm for 1 h, then adding them to the bacterial inoculum and then mixing them with biomass and water by a ratio of 0.5:1:2 which were then kept in the photobioreactor exposed to white light emitting diodes (LEDs) with a luminous flux of 3600 lumen and at 30 °C for 26 days with mixing for 5 min every 30 min to produce biohydrogen. By this method, it is possible to improve the bioenvironmental conditions and the bio-responses of bacteria which results in increasing the biohydrogen yield by 287% over the conventional method.