The highest yield of 96.2 mL/g of hydrogen was recorded under the optimal conditions of 6.21 g/L urea; 0.19 M phosphate-buffered saline (PBS); and 8.74 mL/L of nutrient solution. Meanwhile, approximately 45% of cellulose and 53% of hemicellulose were degraded in the raw corn stalk during H 2 fermentation, implying that the strain FZ11 can directly convert cellulose and hemicellulose into bio-H 2 without substrate pretreatment. A paper on their work appears in the ACS journal Energy & Fuels .

Researchers at Zhengzhou University in China have optimized the process parameters for the direct production of hydrogen from raw corn stalks without substrate pretreatment by a mesophilic (growing in moderate temperatures) hydrogen-producing bacterium, Clostridium sartagoforme FZ11, that they had earlier isolated from cow dung compost.

While the production of bio-hydrogen from biomass via fermentation is of interest due to its cleanliness and renewability, the cellulosic feedstock has required pretreatment before fermentation. A variety of pretreatment methods havebeen tried to degrade the cellulosic substrates into soluble sugars for fermentation, including chemical, physical, and biological methods. All of these have issues, the researchers said, such as high cost or the generation of microbial growth inhibitors such as phenol compounds, organic acids, furfurals, and/or 5-hydroxymethyl-furfural.

Generally, the pretreatment process for the cellulose hydrolysis step is a process of energy consumption and even has to use some corrosive chemicals (such as acid and alkali) or expensive cellulases as well as specialized equipment, which is recognized as the most expensive approach and rate-determining step in the overall H 2 production process, and accounts for about 20% of the total costs. Therefore, the development of breakthrough approaches, including the integration of low-cost saccharification with fermentation, is crucial for bio-H 2 production from cellulosic substrate, is challenging the scientific community, and will break a new path for utilization of cellulose wastes, having attracted more attention than ever.

Among them, one of the strategies for achieving it is to isolate a new strain that can directly use cellulosic feedstock (such as raw corn stalk) to produce H 2 without pretreatment. … In this work, the new strain Clostridium sp. FZ11, which was isolated from a bioreactor feeding raw corn stalk and acclimated compost by microcrystalline cellulose, was employed to produce H 2 from untreated raw corn stalk. —Zhang et al.

To screen the key factors influencing hydrogen production by Clostridium sp. FZ11 from raw corn stalk, the researchers used a Plackett−Burman (PB) design—an approach to optimum multifactorial experiments proposed by R.L. Plackett and J.P. Burman in 1946.

On the basis of single-factor experimental results, the research team screened five independent variables—culture temperature, initial pH, urea, phosphate-buffered saline (PBS), and nutrient solution—and one dummy variable in 12 parallel runs.

The significant independent variables (urea, PBS, and nutrient solution) and their mutual influences on H 2 production were further explored by the Box−Behnken design (BBD)—experimental designs for response surface methodology, devised by George E. P. Box and Donald Behnken in 1960—and response surface analysis.

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