ISOLATION AND CHARACTERIZATION OF PICHIA OCCIDENTALIS MHY1: BIOSURFACTANT-PRODUCING YEAST WITH PLANT GROWTH-PROMOTING TRAITS

The objective of this research is to isolate and evaluate biosurfactant-producing yeasts with beneficial traits for plant growthand to assess their impact on seed germination in selected crops. Five yeast isolates (YHA1, YHA2, MHY1, YHA4, YHA5) were recovered using enriched YEPD and MEA media and characterized based on morphological features. Semi-quantitative screening methods, including emulsification index (EI 24%), oil displacement, microplate assay, and Parafilm M test, were employed to evaluate biosurfactant activity. Among the isolates, MHY1 exhibited the highest emulsification index with kerosene, while YHA1 was most effective with engine oil. MHY3 and YHA5 demonstrated the greatest oil displacement (4.5 cm). All isolates were positive in the microplate and Parafilm M assays, but none tested positive for CTAB.PGP trait screening revealed that MHY1 and YHA5 produced indole-3-acetic acid (IAA), with MHY1 also showing moderate siderophore activity. All isolates were negative for phosphate/zinc solubilization and hydrogen cyanide production. Ammonia production varied, with YHA4 and YHA5 being strong producers. Molecular identification via 18S rRNA sequencing confirmed MHY1 as Pichia occidentalis. FTIR analysis of MHY1’s biosurfactant indicated functional groups characteristic of glycolipids or lipopeptides. Plant growth trials using paddy, pearl millet, and sorghum revealed enhanced germination, seedling vigour, and biomass in seeds treated with MHY1, significantly outperforming controls. MHY1- treated seeds showed the highest seed vigour indices across all crops, suggesting their potential as a plant growth promoter. These findings highlight the dual functionality of MHY1 in biosurfactant production and plant growth promotion, indicating its potential for future use in sustainable agricultural applications.