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 non-hemolytic on blood agar.