Microbial and endogenous origin of fibrinolytic activity in traditional fermented foods of Northeast India

Traditional fermented foods of Northeast India and their associated microorganisms were studied for fibrinolytic activity. A simple and reliable spectrophotometric method to quantify fibrinolytic activity in comparison to conventional fibrin plate assay was established. Out of 31 different types of fermented foods screened, protein rich fermented foods mostly soybean and fish products possessed fibrinolytic activity. Higher fibrinolytic activity was observed in fermented small cyprid fish (Puntius sophore Ham.) products than fermented soybean products. Fibrin zymogram based cluster analysis indicated fibrinolytic activity of endogenous origin in fermented fish products and microbial origin in fermented soybean products. A fermented soybean product Hawaijar showed higher specificity towards fibrin as indicated by fibrinolytic to caseinolytic activity ratio of 3.8 ± 0.21. Identification of 85 fibrinolytic isolates by amplified ribosomal DNA restriction analysis and ribosomal DNA sequencing yielded 15 phylotypes, of which 55% were Bacillus species. Lactic acid bacteria with fibrinolytic activity namely Vagococcus carniphilus, Vagococcus lutrae, Enterococcus faecalis, Enterococcus faecium, Enterococcus gallinarum and Pediococcus acidilactici were identified. Bacillus subtilis, Bacillus amyloliquefaciens, V. carniphilus, V. lutrae and Proteus mirabilis were promising producers of fibrinolytic enzymes with more than 350 plasmin units/mL. The high population of fibrinolytic P. mirabilis found in fermented soybean and pork products might be a serious health concern. Fibrinolytic activity found in fermented food could be partially dependent on the isolated microbes. PCR-DGGE analysis detected uncultivated proteolytic bacteria in both raw material and fermented fish products. These fibrinolytic foods and associated microbial resources could be further explored for novel fibrinolytic therapy.