Isolation of bacterial strains capable of using lupanine, the predominant quinolizidine alkaloid in white lupin, as sole carbon and energy source

Abstract

Seven Gram-negative bacterial strains, capable of using lupanine, the predominant quinolizidine alkaloid in white lupin, as sole carbon and energy source, were isolated from soil in which Lupinus albus and L. luteus had been grown. A metabolic profile system (BIOLOG) identified only three of the seven isolates, two as Xanthomonas oryzae pv oryzae E and one as Gluconobacter cerinus. The maximum specific growth rates of the seven isolates when incubated at 27°C in a medium containing as sole carbon source 2 g L-1 of lupanine, ranged from 0.05 to 0.13 h-l and the concentration of dry biomass at the stationary phase ranged from 0.7 to 1.1 g L-1. Unidentified strains IST20B and IST40D exhibited the highest maximum specific growth rates (0.13 h-1), removed 99% of the initial lupanine after 30 h of incubation, and the dry biomass yields did not exceed 0.4 g per g lupanine consumed. Strain IST20B is of potential use for L. albus debittering because, after 32 h growth in aqueous extracts of L. albus, 85% of initial alkaloids were removed while the concentration of soluble protein was only reduced by 8%.