Microbial production of malic acid from crude glycerol

Abstract

In the last few years, malic acid has received a potential platform for the bio-based chemicals. To replace the traditional methods of malic acid production from petroleum-based compounds such as maleic acid, the efficiency of fermentation technology for malic acid production using fungal species has been improved. Biodiesel is the one of the alternative renewable source of fuel for the fossil fuels. Crude glycerol is generated in huge amount during the process of biodiesel production. Establishment of malic acid production from waste crude glycerol derived from biodiesel production was the foremost aim of this thesis. Initially, a combined resistant on methanol and malic acid strain of Aspergillus niger MTCC281 mutant was generated in solid medium containing methanol (1 5%) and malic acid (40 80 g/L) by the adaptive laboratory evolution process for 22 weeks. The ability of induced Aspergillusniger MTCC281 mutant to use crude glycerol for the production of malic acid was improved. The dry cell weight of the mutant strain on crude glycerol medium was increased by 2.22 times higher than that of the native strain on crude glycerol. The native strain of Aspergillus niger MTCC 281 produced 18.32 + 1.0 g/L of malic acid and the mutant strain of Aspergillus niger MTCC281 produced 59.15 + 1.75 g/L of malic acid from the crude glycerol. When the crude glycerol was used by the mutant strain the produced malic acid was increased by 3.22 times higher than that of the native strain. In addition, the effects of glycerol concentration, spore inoculum concentration, yeast extract concentration and shaking frequency on seed culture morphology of Aspergillus niger PJR1 were investigated. The morphology of Aspergillus niger PJR1 was distorted from pellet form to newline