Immobilization of Photosynthetic Microorganisms for Efficient Hydrogen Production

Microalgal hydrogen production research

“…The solar energy conversion to H 2 efficiency of the immobilized cultures was increased to about 1%, compared with a value of about 0.2% for their free-suspended counterparts, an improvement attributed to optimized irradiance distribution with a better control of the thickness and the concentration of the cells within the entrapment matrix [94]. Entrapment of C. reinhardtii in alginate films was proposed to be a useful method in the screening of transformants for the H 2 -production properties of the different lines [86]. In this vein, Das et al [101] used immobilized C. reinhardtii cells on polyester fabric and sodium alginate hydrogel composites for the development of a horizontal and rectangular microfluidic bioreactor, a so-called artificial leaf device, that allowed for ease of nutrient delivery from the bottom channels of the microfluidic bioreactor and H 2 collection from the headspace.…”

“…A similar setup has been used for the immobilization of either Rhodobacter sphaeroides photosynthetic bacteria (as seen on the current image) [215], or C. reinhardtii microalgal cells [70,80]. The glass plates of the rectangular photobioreactor are held together with binder clips and sealed by applying vacuum grease (image is modified from Tsygankov and Kosourov [86]-reproduced with permission from Wiley); (c) Chlamydomonas reinhardtii are entrapped within square pieces of agar gels with a surface area of about 1 cm 2 . Optical fibers are applied inside these photobioreactors, to serve as an internal light source [216] (image modified from Rashid et al (2013) [216]-reproduced with permission from Springer).…”

“…Immobilization processes can occur either naturally such as in the form of biofilms, or artificially by the attachment of the cells on solid surfaces or entrapment of the cells within matrices [86]. One of the most common ways for the artificial microalgal cell entrapment is the immobilization of the cells within spherical gel lattices, made either of natural (i.e., agar, alginate, carrageenan) or synthetic polymers (i.e., polyacrylamide, polyvinyl alcohol, and polyurethane) [87].…”

“…A high surface-to-volume ratio (S/V) is one of the prerequisites for an efficient photobioreactor [104]. Although vertical column reactors are cost effective, they do not fulfill the requirement of a high S/V ratio; while flat-plate type reactors have the highest S/V ratio needed for an efficient A plastic window/insect-screen is used as the template material for the preparation of algae immobilized alginate films, which was later cut in the form of 1 cm wide strips and then placed within gas-tight sterile glass vials (75 mL) containing 10 mL of growth media [94] (image is modified from Tsygankov and Kosourov [86]-reproduced with permission from Wiley); (b) Photosynthetic cells are immobilized on the surface of a glass-fiber matrix, made of Al-borosilicate glass. A similar setup has been used for the immobilization of either Rhodobacter sphaeroides photosynthetic bacteria (as seen on the current image) [215], or C. reinhardtii microalgal cells [70,80].…”

Hydrogen Photoproduction by Immobilized N 2 -Fixing Cyanobacteria: Understanding the Role of the Uptake Hydrogenase in the Long-Term Process

“…The concept of an artificial leaf has been recognized (28), and approaches for making such a leaf are under development. There are several different techniques that can be considered for further improvements, including natural biofilm formation on translucent matrices and latex coatings (29). Latex coatings (28,30), including the wet coalescence approach (31), are promising methods for the entrapment of phototrophic organisms, but these methods are not usually as efficient as hydrogels for the immobilization of H 2 -producing microalgae and cyanobacteria.…”