Extracellular self-photosensitizer combined with metal oxide-based nano bio-hybrid system encapsulated by alginate improves hydrogen production in the presence of oxygen.

The photocatalytic nano-biohybrid systems have great potential for the conversion of solar energy to fermentative hydrogen production. Herein, a whole-cell nano-biohybrid system consisting of biosynthesized cadmium sulfide, Enterobacter aerogenes cells, and metal oxide nanoparticles was constructed. The system was encapsulated with sodium alginate and used for light-driven biohydrogen production under anaerobic and in the presence of oxygen conditions. After 48 h incubation in the presence of oxygen, the E. aerogenes cells with the encapsulated hybrid system yielded 2.7 mmol H2/mmol glucose, a 13.5-fold higher than that of the E. aerogenes cells without encapsulation. The encapsulated hybrid system could produce hydrogen for up to 96 h and could produce hydrogen even under natural sunlight conditions. These results revealed that efficient hydrogen production is possible in the presence of oxygen. Overall, the present study demonstrated the potential of using proper nano-biohybrid system with encapsulation for the production of hydrogen under ambient air condition.

Microalgal Biorefinery Concepts' Developments for Biofuel and Bioproducts: Current Perspective and Bottlenecks.

Microalgae have received much interest as a biofuel feedstock. However, the economic feasibility of biofuel production from microalgae does not satisfy capital investors. Apart from the biofuels, it is necessary to produce high-value co-products from microalgae fraction to satisfy the economic aspects of microalgae biorefinery. In addition, microalgae-based wastewater treatment is considered as an alternative for the conventional wastewater treatment in terms of energy consumption, which is suitable for microalgae biorefinery approaches. The energy consumption of a microalgae wastewater treatment system (0.2 kW/h/m3) was reduced 10 times when compared to the conventional wastewater treatment system (to 2 kW/h/m3). Microalgae are rich in various biomolecules such as carbohydrates, proteins, lipids, pigments, vitamins, and antioxidants; all these valuable products can be utilized by nutritional, pharmaceutical, and cosmetic industries. There are several bottlenecks associated with microalgae biorefinery. Hence, it is essential to promote the sustainability of microalgal biorefinery with innovative ideas to produce biofuel with high-value products. This review attempted to bring out the trends and promising solutions to realize microalgal production of multiple products at an industrial scale. New perspectives and current challenges are discussed for the development of algal biorefinery concepts.

High potential of Rhizopus treated rice bran waste for the nutrient-free anaerobic fermentative biohydrogen production.

In this study, Rhizopus oligosporus MTCC 556 (Rhizopus) treated rice bran was utilized for the anaerobic bacterial fermentative hydrogen production. The Enterobacter aerogenes MTCC 2822 with nutrients addition fermented the treated rice bran to give hydrogen yield of 5.4 mmol H2/g of biomass. A closely similar hydrogen yield of 4.6 mmol H2/g of biomass was obtained from the treated rice bran under the condition without nutrients addition, suggesting the potential of the fungus treatment to produce hydrogen from nutrient-free fermentation. The pretreated rice bran showed efficient hydrogen production upon anaerobic fermentation without nutrients addition. The Rhizopus pretreated biomass can provide required nutrients for the enhancement of hydrogen yield by anaerobic fermentation. The Rhizopus pretreatment of rice bran enhanced the hydrogen production under nutrient-free conditions which reduced the overall production cost. The findings provide a promising solution to efficiently utilize the rice bran waste for low cost hydrogen production.

Encapsulated titanium dioxide nanoparticle-Escherichia coli hybrid system improves light driven hydrogen production under aerobic condition.

Utilizing light energy for hydrogen production by combining nano-bio inspired photosynthetic system has received remarkable attention in renewable energy production. In this study, we applied a sodium alginate encapsulation strategy to our previously developed nano-bio hybrid system for photocatalytic hydrogen production under aerobic condition by combining the inorganic semiconductor titanium dioxide (TiO2), electron mediator methylviologen (MV2+), along with E. coli (hydrogenases) in an encapsulated system under the given light intensity of 2000 W m-2 and its hydrogen production efficiency was studied. Under aerobic condition the encapsulated hybrid system produced hydrogen (2.4 mmol H2/ mmol glucose) 3-fold higher than the unencapsulated hybrid system (0.8 mmol H2/ mmol glucose), suggesting that encapsulation is essential to protect oxygen sensitive hydrogenase under aerobic condition. The encapsulated hybrid system was also feasible under direct sunlight for hydrogen production. Overall, this study could serve as a new strategy for biological hydrogen production under aerobic condition.