Production of Sodium Gluconate from De-Lignified Corn Cob Residue by On-Site Produced Cellulase and Co-Immobilized Glucose Oxidase and Catalase

Significance Statement

A wide range of products can be obtained from lignocellulosic materials, such as butanol, ethanol and other organic acids, via enzymatic hydrolysis or microbial fermentation. Despite being a suitable substitute for starch or glucose used as raw materials in fermentation industry, lignocellulose hydrolysate often contains substances that inhibit microbial growth which contributes to longer fermentation periods. Consequently, many fermentation industries keep off application of lignocellulose. Sodium gluconate can be used as a chelating agent, surface cleaning of steel or glass and as a high-efficiency retarder and superplasticizer in the concrete industry. The presence of a carboxyl group instead of an aldehyde group in the structure of gluconic acid differentiates it from that of glucose. Gluconic acid is mainly produced through microbial fermentation. The enzymes, glucose oxidase and catalase have also been seen sufficient to effectively catalyze the production of gluconic acid from glucose in vitro. In this work, enzymatic conversion of de-lignified corn cob residue has been explored.

Researchers led by Professor Yinbo Qu from the State Key Laboratory of Microbial Technology, at Shandong University in China studied the feasibility of production of sodium gluconate from de-lignified corn cob residue using in situ generated cellulace and co-immobilized glucose oxidase and catalase. Their research work is now published in the peer-reviewed journal, Bioresource Technology.

The research team commenced their empirical procedure by on-site production of cellulace that would later be used for lignocellulose saccharification. Penicillium oxalicum I1-13 was used for the production of cellulace with high β-glucosidase activity. A fed-batch saccharification process was developed to obtain high yields of glucose. Eventually, glucose oxidase and catalase were co-immobilized to catalyze de-lignified corn cob residue hydrolysate to produce sodium gluconate.

The authors observed that a certain concentration of glucose was obtained by fed-batch saccharification of de-lignified corn cob residue. The team was also able to produce certain concentrations of sodium gluconate by co-immobilizing glucose oxidase-catalase under optimal conditions. As the reusability of the immobilized enzyme was under way, the team realized that as the reusing increased, the residual enzyme activities decreased gradually. This was attributed to the breakage of immobilized enzyme particles and inactivation of immobilized enzymes during the conversions. In total the team was able to produce 20.53g of sodium gluconate using one milligram of enzymes after six times of conversion.

The study provides a potential route for the production of valuable chemicals by enzymatic conversion of lignocellulosic materials. Under the optimized conditions, de-lignified corn cob residue hydrolysate containing glucose has been obtained and sodium gluconate has been produced by co-immobilized glucose oxidase-catalase. This co-immobilized glucose oxidase-catalase has been seen to maintain over 60% activity after being reused for 6 times. Taken together, enzymatic production of sodium gluconate from lignocellulose hydrolysate proposed here has a great potential for industrial production of sodium gluconate.

About The Author

Dr. Yinbo Qu graduated on industrial microbiology at Shandong University in 1974, and received his MS and PhD degrees in microbiology at the same university in 1982 and 1986, respectively. He was employed by Shandong University as assistant professor in 1981, and was promoted to a full professor in 1993. Prof. Qu had served the State Key Laboratory of Microbial Technology as its director from 1997 to 2013, and served the School of Life Science as its dean from 2001 to 2013. He was elected as Vice President of Chinese Society for Microbiology in 2006-2016 and Advisory Board Member of Asia Federation of Biotechnology (AFOB) in 2010-2016. He worked as a graduate student at Osaka University and The University of Tokyo (1981-1982) for one year, and as a visiting scholar at Lund University (1993-1994) and Kyoto University (1998-1999).

His research interests are focused on biodegradation and bioconversion of lignocellulosic biomass resources by microorganisms. He has coauthored more than 370 articles and 12 books and licensed 13 patents. He was awarded Second Prize of National Science and Technology Achievement in 2005 and Second Prize of National Technology Invention in 2011. As the Chief Scientist, his research on fundamentals underlying bioconversion of lignocellulosic biomass was granted by the National Basic Research Program (973 Program).

About The Author

Xiaolong Han received his Ph.D. degree in fermentation engineering from State Key Laboratory of Microbial Technology, Shandong University, China in 2017. His research interest includes improving fungal cellulase productivity and developing novel technologies to produce valuable chemicals from lignocellulosic materials.

Reference

Xiaolong Han, Guodong Liu, Wenxia Song, Yinbo Qu. Production of Sodium Gluconate from De-Lignified Corn Cob Residue by On-Site Produced Cellulace and Co-Immobilized Glucose Oxidase and Catalase. Bioresource Technology (2017).

 

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