Use of Protein Hydrolysate from Yellow Stripe Trevally (Selaroides leptolepis) as Microbial Media

The objective of this study was to investigate the potential use of protein hydrolysate from yellow stripe trevally as a nitrogen source for the growth of different microorganisms. Protein hydrolysates from yellow stripe trevally with different degrees of hydrolysis (5, 15 and 25%) prepared using Alcalase (HA) or Flavourzyme (HF) were determined in comparison with commercial Bacto Peptone. For bacteria, Staphylococcus aureus and Escherichia coli, HF with 25% DH (HF ₂₅) yielded the highest cell density and specific growth rate (μ _max) and the lowest generation time (t _d) (p < 0. 05). For yeasts, Saccharomyces cerevisiae and Candida albicans, Bacto Peptone yielded the higher growth rate than did HA and HF (p < 0. 05), whereas no differences in μ _max and t _d were observed for fungus, Aspergillus oryzae (p > 0. 05). The pH of culture broth containing HF ₂₅ decreased markedly during the first 8 hours of cultivation of S. aureus and E. coli (p < 0. 05). This directly lowered the colony size of S. aureus (p < 0. 05). However, buffered culture broth containing HF ₂₅ rendered the similar growth and colony size of S. aureus (p > 0. 05), compared with that containing Bacto Peptone. Scanning electron microscopic study revealed no differences in size and shape of microorganisms cultured in HF ₂₅ and Bacto Peptone (p > 0. 05).