Methods of Random Mutagenesis of Aspergillus Strain for Increasing Kojic Acid Production

: Kojic acid is an organic acid that is commonly used in the pharmaceutical and cosmetic industries. This acid compound is a secondary metabolite produced by various microorganisms, one of which is Aspergillus oryzae. Typically, improving the strain can enhance kojic acid production. A mutation is one of the tools to perform strain improvement because the change in kojic acid-producing genes effectively increases kojic acid yield. Random mutagenesis is a classic approach for inducing and producing mutants with random mutations. The mutagenesis can be generated by the individual physical and chemical mutagen, combined physical and chemical mutagens, or initiate by protoplast preparation. Aspergillus strains that are exposed to physical mutagens (e.g., UV) or chemical mutagens (e.g., N-methyl-N-nitro-N-nitrosoguanidine (NTG)) showed their abilities in increasing kojic acid production. Several new mutation methods, such as Ion Beam Implantation and Atmospheric and room temperature plasma (ARTP), also showed good responses in enhancing the production of biological products such as kojic acid. This review compared different random mutagenesis methods of Aspergillus strain with various mutagen types to provide better insight for researchers in choosing the most suitable method to increase kojic acid production.

A Novel Protein AoHPS1 Is Involved In Oxidative Stress and Kojic Acid Synthesis in Aspergillus Oryzae

Aspergillus oryzae usually suffers from oxidative stress during the process of aerobic fermentation. However, there is little information on what genes involve in oxidative stress of A. oryzae. Here, we found that the expression of a novel gene Aohps1 was induced during the growth and development of A. oryzae with and without oxidative stress. Sequence analysis revealed that Aohps1 has four transmembrane regions and is conserved in Aspergillus species. Overexpression and deletion of Aohpi1 caused the growth defects with and without oxidative stress, including mycelium growth, conidia formation and biomass. Meanwhile, the Aohpi1 overexpression strain exhibited more sensitivity to oxidative stress than the Aohpi1 disrupted mutant. Furthermore, overexpression and disruption of Aohps1 resulted in the inhibition of kojic acid production with and without oxidative stress, consistent with the reduced expression of kojA that directly contributed to the synthesis of kojic acid. Additionally, the yield of kojic acid is less in the Aohps1 overexpression strain than in the Aohps1 deletion mutant under oxidative stress. Collectively, the discovery of Aohps1 provides new insights into oxidative stress and kojic acid synthesis in A. oryzae.

Screening and optimization of submerged fermentation of aspergillus species for kojic acid production

Kojic acid is organic acid obtained from numerous species of Aspergillus through fermentation.This is among most demanding substances in cosmetic industries as an alternate to carcinogenic Hydroquinone and has grabbed a vital position in Pharmaceuticals, Food and Agriculture industries. Current experimental approach was designed for production and purification of Kojic acid crystals from A. flavusand A.oryzae and measured the effects of pH, temperature, static and non-static (shaker) condition on Kojic acid yield in submergedfermentation. Significant yield of Kojic acid crystal was obtained by A. flavusas compared to A. oryzae. Optimized conditions were pH 4.5 for (A. flavus) and 3.5 for (A. oryzae) at 30 0Cwith 20 days of incubation. High yield of Kojic acid crystals were produced under static condition (16 g/L in A. flavusand 11 g/L in A.oryzae) in contrast to non- static (shaker) conditions (6 g/L in A. flavusand 5 g/L in A. oryzae). Quantitative estimation of Kojic acid was done through Bentley’s colorimetric method followed by TLC, FTIR and HPLC. This analysis was found successful after achieving the high yield of Kojic acid under optimized conditions.