Growth behavior of different lactic acid bacteria in lupin flour and lupin protein isolate

All over the world, fermented foods play a major role in the human diet. Besides food preservation, a number of advantages are linked with the fermentation process like improved flavor and digestibility or reduction of antinutritives1,2. In contrast to soy, the fermentation of lupin, a high protein and high nutritive legume3, has not been studied extensively so far. Especially research information on the interaction of secondary plant metabolites with microorganisms is scare. To contribute to this, the objective of this study is to investigate the fermentation performance of different lactic acid bacteria on lupin containing substrates (L. angustifolius cv. boregine). The metabolism of Lactobacillus (Lb.) plantarum, Bifidobacterium (B.) animalis ssp. lactis, Pediococcus (P.) pentosaceus and Lactococcus (L.) lactis ssp. lactis was investigated at their respective optimum growth temperature on a 10% lupin flour (LF) and 10% lupin protein isolate (LPI) suspension. Carbohydrate content (10%) and composition (mainly sucrose, raffinose and stachyose) of the protein suspension was thereby adjusted to that of lupin flour. Growth behavior including the competitiveness of the strains tested by statistical MALDITOF MS analysis of microbiota, lactate/acetate production and sugar utilization (analyzed by HPAEC) was evaluated. Fermentation experiments revealed that all selected microorganisms were able to grow and metabolize sugars on LF in the same order of magnitude as on LPI. In comparison, the growth rate of B. animalis ssp. lactis was slightly higher in LPI suspension and greater amounts of organic acids (+51.1% lactate, +51.2% acetate) were produced. On the contrary, Lb. plantarum showed a significantly higher metabolism activity on LF and L. lactis ssp. lactis was only dominant in the flour sample. Moreover, fermentation performance of P. pentosaceus was not significant different (p>0.05) on the two substrates. In conclusion, fermentation behavior of the studied microorganisms was apparently not influenced by the secondary plant metabolites occurring in lupin flour used in this study.