Abstract

The present research work was aimed to screen the endophytic fungal pigment against human pathogenic bacteria and optimize the most suitable medium with specific pH, temperature and elicitors to improve the growth and antimicrobial pigment production. Based on the morphological characters, the isolated strain SVJM139 was identified as Monodictys castaneae SVJM139. Among 13 media tested (Table 1), Czapek yeast extract agar/Czapek yeast extract broth (CYA/CYB) was the best suitable medium. Optimized CYA/CYB with specific pH (5), temperature (24°C) and silver nitrate (15 mg/l) strongly influenced the highest fresh weight (23.7 ± 0.4^a g/l), dry weight (3.7 ± 0.0^a g/l), radial growth (8.9 ± 0.1^a cm) and pigment production (193 ± 2.2^a µg/g) on 18^th day when compared to normal CYA/CYB. Antimicrobial activity of the M. castaneae SVJM139 pigments (75 µg/ml) significantly inhibited the growth of human pathogenic bacteria viz., Staphylococcus aureus (21.4 ± 0.34^a mm), Klebsiella pneumoniae (20.0 ± 0.32^a mm), Salmonella typhi (20.3 ± 0.32^a mm) and Vibrio cholerae (20.7 ± 0.33^a mm). The present findings concluded that M. castaneae SVJM139 pigment was clearly more active than the commercial antibiotic, streptomycin. Our literature survey suggests that this is the first report of the new endophytic M. castaneae SVJM139 pigment with anti-microbial activity against human pathogens.

Key words: Antimicrobial activity, fungal pigment, Monodictys castaneae,optimization.