Biological hydrogen production using co-culture versus mono-culture system

Abstract

2015): Biological hydrogen production using co-culture versus mono-culture system, Environmental Technology Reviews, In coming years, the generation of organic wastes will exceed 250 billion tonnes worldwide. The organic wastes offer plentiful source of readily available and inexpensive substrates for fermentative hydrogen production. A sustainable approach for hydrogen production from various methods, such as photo-, dark fermentation and sequential two-stage has significant advantages to complement traditional process. During hydrogen fermentation, defined, well-characterized and composite microorganisms are studied. Substantial research efforts have been carried out to increase hydrogen production by using co-culture system, which offers advantage of increased H 2 yield and production rate in comparison with mono-culture. The concept of co-culture system is a simple step of mixing different microbial strains for improving the individual properties that other strain lacks. Co-culture system is cost-effective, which potentially eliminates pretreatment step and avoids the use of expensive reducing agent. By eliminating these two steps, the overall process cost can be reduced without negotiating the hydrogen yield. The co-culture system directly hydrolyses complex organic substrates into fermentable sugar with 94.1% improved yield in comparison with mono-culture. Co-culture offers various advantages, example, reduction in lag phase, resistance to environmental fluctuations and provides stability with uninterrupted hydrogen production rate, which is eight times in comparison with mono-culture. The co-culture system of hydrogen production is also an alternative effluent treatment method with 60% reduction in the chemical oxygen demand level and can be easily integrated into a pilot scale to achieve continuous H 2 production. The elaboration on co-culture system suggests a huge potential of hydrogen production using complex organic wastes with viable application towards industrialization.

Seed Pretreatment for Increased Hydrogen Production Using Mixed-Culture Systems with Advantages over Pure-Culture Systems

“…The initial pH affects the activity of the iron-containing hydrogenase enzyme, extends lag phase, affects the rate of biochemical processes and also affects the metabolic pathways during the fermentation of hydrogen production [40,48]. Acidic pH of 5-6 is optimum for hydrogen production, a decrease and increase from the optimum pH results in a metabolic shift with the production of volatile fatty acids (VFA) [58,132]. Similarly, low biomass concentration can cause a delayed lag time with slow fermentation rates and in case of high concentration will have adverse effects on rates and yields of by-products [40].…”

Selection and modification of microorganisms and substrates for acquiring and separation of energy carriers

“…Thermophiles are the closest for hydrogen production to the theoretical yield by overwhelming thermodynamic barrier, but these strains have to be cultivated at elevated temperature with high energy requirements [33]. Hydrogen research strategies organism-wise stated that productive pure cultures were used with defined substrate as the carbon source, but mixed cultures are preferred for operational ease and process stability [35]. When wastewater or agricultural waste is used as the substrate, a mixed microbial population is more favorable and practical [36].…”

Enrichment of Secondary Wastewater Sludge for Production of Hydrogen from Crude Glycerol and Comparative Evaluation of Mono-, Co- and Mixed-Culture Systems

“…Biodiesel and biohydrogen are considered as renewable, efficient and carbon dioxide (CO 2 )-free fuel of choice for the future [ 1 , 2 ]. Biodiesel production across the world is increasing rapidly and estimated to reach 20 billion liters in 2020 due to strong government policies and incentives across the world [ 3 , 4 ]. About 100 kg of crude glycerol (CG) is generated as waste by-product with every ton of biodiesel produced [ 5 ].…”

“…Sustainable production and commercialization of biodiesel depends on the demand and increased utilization of CG [ 3 ]. With presence of various impurities across CG, refining for glycerin is no longer cost-effective with decreasing market value for glycerin [ 4 , 6 ]. Value added utilization (valorization) of waste CG into biofuels or biochemical for additional market value represents a promising route with several advantages [ 7 , 8 , 9 ].…”

“…Initial experiments at different temperatures were evaluated in this study. Optimization of fermentation parameters using statistical tools such as Central Composite Design (CCD) narrow down experimental runs, suggest the optimum parameter range and identify the dominant parameter responsible for H 2 production in fewer runs [ 4 , 15 ]. The parameters needed for optimization are the substrate concentration, media supplements, endo-nutrients, inoculum size and the fermentation pH [ 8 , 12 , 27 ].…”