Sourcing Starter Cultures for Parkia biglobosa Fermentation Part II: Potential of Bacillus subtilis Strains.

ABSTRACT

Aim: To select good strains of Bacillus subtilis for use as starter culture in the fermentation of Parkia biglobosa. Study Design: Fifteen (15) strains of Bacillus subtilis group obtained from commercial samples were used in starter-culture fermentation of Parkia biglobosa seeds to produce ‘iru’. Place and Duration of Study Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pahumthani, Thailand, between March to May 2010. Methodology: The quality of the starter culture-fermented products were compared on the bases of sensory evaluation, degree of hydrolysis (DH), level of ammonia nitrogen (NH3-N), pH and enzymatic activities. The 15 strains were also screened for haemolytic activity. Results: On the basis of the sensory scores of 5 parameters (color, odor, consistency, texture and over-all liking), particularly the over-all liking, 5 strains were rated the best (in descending order) BC4333 > 8B > 2B > 7A > 5A, amongst the 15 tested. There were good correlations between pH and DH (r= 0.926), DH and NH3-N (r=0.962) and between pH and NH3-N (r=0.945). The strain BC4333 produced the very soft variant of ‘iru’ (‘iru-pete’), without the addition of ‘kuuru’ (local potash). The quantity of extracellular enzymes (protease, amylase, pectinase, phytase and lipase) produced during fermentation varied significantly. None of the 5 strains was haemolytic on sheep blood agar. Conclusion: The 5 strains of Bacillus subtilis (BC4333, 8B, 2B, 7A, 5A) that showed potentials of being used as starter cultures for industrial production of ‘iru’, were nonhemolytic on blood agar.