Photo-fermentational hydrogen production of Rhodobacter sp. KKU-PS1 isolated from an UASB reactor

Abstract

Background: In this study, the detection of nifH and nifD by a polymerase chain reaction assay was used to screen the potential photosynthetic bacteria capable of producing hydrogen from five different environmental sources. Efficiency of photo-hydrogen production is highly dependent on the culture conditions. Initial pH, temperature and illumination intensity were optimized for maximal hydrogen production using response surface methodology with central composite design. Results: Rhodobacter sp. KKU-PS1 (GenBank Accession No. KC478552) was isolated from the methane fermentation broth of an UASB reactor. Malic acid was the favored carbon source while Na-glutamate was the best nitrogen source. The optimum conditions for simultaneously maximizing the cumulative hydrogen production (H max ) and hydrogen production rate (R m ) from malic acid were an initial of pH 7.0, a temperature of 25.6°C, and an illumination intensity of 2500 lx. H max and R m levels of 1264 ml H 2 /l and 6.8 ml H 2 /L-h were obtained, respectively. The optimum initial pH and temperature were further used to optimize the illumination intensity for hydrogen production. An illumination intensity of 7500 lx gave the highest values of H max (1339 ml H 2 /l) and R m (12.0 ml H 2 /L-h) with a hydrogen yield and substrate conversion efficiency of 3.88 mol H 2 /mol malate and 64.7%, respectively. Conclusions: KKU-PS1 can produce hydrogen from at least 8 types of organic acids. By optimizing pH and temperature, a maximal hydrogen production by this strain was obtained. Additionally, by optimizing the light intensity, R m was increased by approximately two fold and the lag phase of hydrogen production was shortened.

Biological and Bioelectrochemical Systems for Hydrogen Production and Carbon Fixation Using Purple Phototrophic Bacteria

“…Na-glutamate enhanced the PPB growth and hydrogen production rate (2.1-2.7 mLH 2 /Lh). The results of this study are in agreement with those reported by other researchers, who have shown that Na-glutamate enhances hydrogen production without inhibiting the nitrogenase enzyme (Melnicki et al, 2008;Assawamongkholsiri and Reungsang, 2015). This is due to the fact that organic nitrogen can be directly assimilated into proteins and a less complex metabolic activity is required for the production of amino acids compared to inorganic sources (Merugu et al, 2010).…”

“…It was observed that the use of malic acid as carbon source achieved the highest hydrogen production (H 2_max , mLH 2 /L) and the highest H 2 production rate (H 2_rate , mLH 2 /Lh; Table 2). Malic acid has widely used as optimum carbon source for H 2 production, probably due to its capacity to directly enter the tricarboxylic acid cycle (Melnicki et al, 2008;Kim et al, 2012b;Assawamongkholsiri and Reungsang, 2015). Other evidences supporting malic acid as the optimum organic to conduct hydrogen production is shown in Supporting Information.…”

“…The first set of experiments were conducted by using 2 gCOD/L of L-malic acid as the carbon source. Malic acid was chosen as a suitable carbon source that could favor hydrogen production by PPB (Assawamongkholsiri and Reungsang, 2015). Batch experiments were performed using: inorganic (NH 4 Cl) and organic (Na-glutamate) nitrogen, both with concentrations of 75, 150, and 300 mgN/L, and finally dinitrogen gas (60 mL of N 2 in the headspace).…”

Photo-hydrogen and lipid production from lactate, acetate, butyrate, and sugar manufacturing wastewater with an alternative nitrogen source byRhodobactersp.KKU-PS1

“…Purple non-sulfur photosynthetic bacteria (PNSB) such as Rhodobacter sphaeroides KKU-PS5, R. sphaeroides KD131, R. sphaeroides O.U. 001, and Rhodopseudomonas palustris WP3-5 have the capacity to convert hydrogen from a single organic acid (Assawamongkholsiri, Plangklang & Reungsang, 2016; Assawamongkholsiri & Reungsang, 2015; Laocharoen & Reungsang, 2014) and mixed volatile fatty acids (VFAs), which are the major substrates in dark fermentation effluents (Lo et al, 2011; Uyar et al, 2009; Yang et al, 2012). Moreover, a variety of wastewaters such as brewery wastewater (Hay et al, 2017; Seifert, Waligorska & Laniecki, 2010a), dairy wastewater (Seifert, Waligorska & Laniecki, 2010b), sugar industry wastes (Assawamongkholsiri et al, 2018; Keskin & Hallenbeck, 2012) and effluent from dark fermentation processes (Argun, Kargi & Kapdan, 2008; Ozmihci & Kargi, 2010; Sagnak & Kargi, 2011) can be used by PNSB.…”

Hydrogen Production by Photo Fermentation via Rhodobacter sp.

“…pH is a very important factor that influences the metabolism. The active site and the characteristics of the biochemical reaction of the enzyme nitrogenase, the enzyme responsible for the production of hydrogen, have been affected by its ionic form at different pH values in the culture medium [4].…”