Long-term biological hydrogen production by agar immobilized Rhodobacter capsulatus in a sequential batch photobioreactor

Abstract

In this study, agar immobilization technique was employed for biological hydrogen production using Rhodobacter capsulatus DSM 1710 (wild type) and YO3 (hup-mutant) strains in sequential batch process. Different agar and glutamate concentrations were tested with defined nutrient medium. Agar concentration 4% (w/v) and 4 mM glutamate were selected for bacterial immobilization in terms of rate and longevity of hydrogen production. Acetate concentration was increased from 40 to 60-100 and 60 mM gave best results with both bacterial strains immobilized in 4% (w/v) agar. Cell concentration was increased from 2.5 to 5 mg dcw mL agar and it was found that increasing cell concentration of wild-type strain caused decrease in yield and productivity while these parameters improved by increasing cell concentration of mutant strain. Also, the hydrogen production time has extended from 17 days up to 60 days according to the process conditions and parameters. Hydrogen production by immobilized photosynthetic bacteria is a convenient technology for hydrogen production as it enables to produce hydrogen with high organic acid concentrations comparing to suspended cultures. Besides, immobilization increases the stability of the system and allowed sequential batch operation for long-term application.

Immobilisation of Selected Bacteria for Remediation on Various Media

“…The highest number of microorganisms in the soil for the applied bacterial consortium immobilized on alginate with 50% (v/v) of biocarbonate was noted in the conducted studies. Similar results were obtained in Eklahout et al, where positive effects of immobilization of Rhodobacter capsulatus using agar on pH stability during the process were documented [23]. Immobilized bacteria also impact on the control of phytopathogenic fungal populations [24].…”

“…on alginate, acrylamide [17], 3-chloroaniline [18] and 2-chloroethanol [19]. Frequently used media also include polyurethane [20], agar [21][22][23] and kappa-carrageenan [24]. The highest number of microorganisms in the soil for the applied bacterial consortium immobilized on alginate with 50% (v/v) of biocarbonate was noted in the conducted studies.…”

Microalgal Hydrogen Production

“…Aerobic photosynthesis occurs in higher plants, algae and cyanobacteria, while anaerobic photosynthesis occurs in organisms such as green sulfur and purple nonsulfur bacteria. [41] Therefore, facultative anaerobic organisms capable of decomposing water and releasing hydrogen are preferred, such as algae and cyanobacteria.…”

“…However, anaerobic organisms need to obtain electrons from electron donor substrates such as H 2 S or organic acids, rather than water, so their application is not commercially viable in terms of large‐scale hydrogen photoproduction. Aerobic photosynthesis occurs in higher plants, algae and cyanobacteria, while anaerobic photosynthesis occurs in organisms such as green sulfur and purple nonsulfur bacteria . Therefore, facultative anaerobic organisms capable of decomposing water and releasing hydrogen are preferred, such as algae and cyanobacteria.…”

A Mediated BOD Biosensor Based on Immobilized B. Subtilis on Three-Dimensional Porous Graphene-Polypyrrole Composite

“…Microorganism immobilization may provide an effective and economical method in solving the aforementioned problems, and additionally, immobilization can offer other benefits, such as improved metabolic activities, greater stability by minimizing bacterial loss toxic compounds and increased protection against environmental toxicity of pollutants [ 8 ]. According to the reported documents, a variety of materials including calcium alginate [ 9 ], agar [ 10 ], cellulose [ 11 ], and polyvinyl alcohol (PVA) [ 12 ], and so forth, have been prepared in various geometric formats and used to immobilize microorganisms. In recent years, the three-dimensional (3D) porous structure of graphene is significantly attractive for its biosensor application due to its 3D interconnected porous structure and excellent mechanical stability from the strong π-π stacking of graphene sheets [ 13 , 14 ].…”