Citric acid production by Aspergillus niger on wet corn distillers grains

Abstract

Aims: To determine which citric acid‐producing strain of Aspergillus niger utilized wet corn distillers grains most effectively to produce citric acid. Methods and Results: Citric acid and biomass production by the fungal strains were analysed on the untreated grains or autoclaved grains using an enzyme assay and a gravimetric method respectively. Fungal citric acid production on the grains was found to occur on the untreated or autoclaved grains. The highest citric acid level on the grains was produced by A. niger ATCC 9142. The autoclaved grains supported less citric acid production by the majority of strains screened. Biomass production by the fungal strains on the untreated or autoclaved grains was quite similar. The highest citric acid yields for A. niger ATCC 9142, ATCC 10577, ATCC 11414, ATCC 12846 and ATCC 26550 were found on the untreated grains. Treatment of the grains had little effect on citric acid yields based on reducing sugars consumed by A. niger ATCC 9029 and ATCC 201122. Conclusions: It is feasible for citric acid‐producing strains of A. niger to excrete citric acid on wet corn distillers grains whether the grains are treated or untreated. The most effective citric acid‐producing strain of A. niger was ATCC 9142. Significance and Impact of the Study: The study shows that the ethanol processing co‐product wet corn distillers grains could be utilized as a substrate for the commercial production of citric acid by A. niger without treatment of the grains.

Biotechnological production of citric acid

“…For instance, CA production by solid-state fermentation of kiwifruit peel by A. niger ATCC 9142 significantly decreased after supplementation with 0.74 mmol methanol/l (27), and Tsay and To (103) reported that methanol inhibited both A. niger TMB 2022 growth and CA production. Similar findings were reported by other authors (4, 71, 109). …”

Recent Advances in Citric Acid Bio-production and Recovery

“…The substrates include sugarcane bagasse, fruit pomace, wheat, rice, maize and grain brans, wheat and rice straw, coconut coir pith, newspaper, fruit wastes, tea and coffee wastes, cassava waste, and distiller grains among others (Krishna andChandrasekaran 1995, 1996;Hang and Woodams 2000;Vandenberghe 2000;Gowthaman et al 2001;Pandey et al 2001;Shojaosadati and Babaeipour 2002;Kumar et al 2003;Xie and West 2006;Karthikeyan and Sivakumar 2010;Kuforiji et al 2010).…”

Plant Biomass from Grasses: An Underutilized Feedstock for Microbial Production of Chemicals and Biopolymers

“…Polysaccharide gums, such as pullulan or curdlan, can be synthesized from glucose by microorganisms [8,9] The literature examining microbial specialty chemical or biopolymer production from grass hydrolysates is extremely limited. It has been shown that hydrolysates of plant biomass can support fungal citric acid production by Aspergillus niger or fumaric acid production by Rhizopus oryzae using solid-state fermentation [10,11]. Also, a xylanase hydrolysate of the grass big bluestem supported the production of xylitol by Candida species [7].…”