Two-way strategy for enhanced pectinase production: Random mutagenesis and utilization of a halophytic biomass

Abstract

Strain improvement through mutagenesis has remained an effective strategy for the cost-effective production of industrially important enzymes. Here, we focused on random mutagenesis of a pectinolytic yeast, Geotrichum candidum AA15, and on utilization of halophytic biomass along with apple waste as substrate for pectinase production to make the process cost effective. G. candidum AA15 was treated with a physical (UV) and a chemical (Ethidium bromide) mutagen separately and in a sequential way. After mutagenic treatments, a total of eight mutants (AHU0 to AHU5, AHC1 and AHUC) were obtained and assessed for pectinase production but a mutant strain (AHC1) yielded the highest pectinase production of 12.03 IU mL−1 which was >2 folds higher than the wildtype strain. The reason for positive effect of mutagenesis on pectinase production was investigated, however, the gene encoding polygalacturonase in the mutant strains was found similar to that of the wildtype strain. The purified pectinase from the mutant strains also shared molecular mass of 60–66 kDa with the wildtype. The mutant strain's cell density was higher than the wildtype and it can be linked with the higher productivity of pectinase reported in this study. The mutant strain, AHC1, yielded 8.32 IU mL−1 and 6.35 IU mL−1 of pectinase after the fermentation of apple peels and biomass from a halophytic plant, Cressa cretica, respectively. The utilization of the substrate was observed through Scanning Electron Microscopy. Thus, the study established a path to proceed for cost effective pectinase production through strain improvement and utilization of crude substrates.