Solid-state fermentation with Bacillus subtillis co-cultured with probiotic Lactobacillus spp. enhances the bioactive peptides, nutritional and antioxidative potentials of tamarind seed

Abstract

The effect of natural or controlled solid-state fermentation using single or mixed probiotic strains on the nutritional, bioactive and phytochemical constituents, and antioxidant activities of tamarind seeds was evaluated. Tamarind seeds were subjected to either controlled solid-state fermentation (37 °C, 72 h) using either Bacillus subtilis only or Bacillus subtilis co-cultured with probiotics Lactobacillus spp. (Lactobacillus fermentum, Lactobacillus rhamnosus GG, Lactobacillus brevis, and Lactobacillus delbrueckii) or natural fermentation while unfermented tamarind seeds served as control. The changes in the nutritional composition, peptide content, antioxidative properties (Ferric reducing antioxidant power (FRAP) and DPPH radical scavenging activities) and total viable count of probiotics in fermented tamarind seed were evaluated using standard methods. The peptide content, crude protein, fat, and fibre (100.19 mg/g, 51.35, 9.50 and 5.10%), and FRAP and DPPH (0.55 and 21.60%) in unfermented tamarind seed were significantly (p < 0.05) lower than fermented tamarind seed (271.00–308 mg/g, 12, 62.84–64.02, 12.21–13.11 and 6.01–6.90, and 1.42–2.92 and 26.66–35.70%, respectively), after 72 h of fermentation. The total viable count in the tamarind seed fermented with Bacillus subtilis only was 1.2 × 10⁹ CFU/g while that co-cultured with probiotics ranged from 6 × 10⁸ to 9.9 × 10⁸ CFU/g after 72 h of fermentation. This study showed that a controlled solid-state fermentation using probiotics Lactobacillus co-cultured with Bacillus subtilis can significantly increase the peptide contents, and enhance the nutritional and antioxidant activities of tamarind seed while producing a condiment with significant probiotic potential.