Production of flavour precursors byPenicilliumcandidum using selected polyunsaturated fatty acids

Abstract

Biomass of Penicillium candidum was harvested and homogenized prior to centrifugation. The resultant supernatant, considered as the crude enzymatic extract, was enriched by ammonium sulphate precipitation. The enriched enzymatic extract was assayed for its lipoxygenase (LOX) activity, using selected polyunsaturated fatty acids (PUFAs) as substrates. Two pH optima for LOX activity were determined at 6.0 and 8.5. The results indicated a wide range of LOX activity towards free PUFAs, including linoleic, linolenic and arachidonic acids, as well as preferential substrate specificity towards linoleic acid over its alkyl esters. The catalytic efficiency values, defined as the ratio V max :K m , were 214, 163 and 160 for linolenic, linoleic and arachidonic acids, respectively. It was shown that the LOX activity produced many monohydroperoxy regio-isomers of the PUFAs, and there was a predominance of conjugated diene hydroperoxides. Significant production (16%) of the unconjugated 10-hydroperoxides of octadecadienoic acid (HPOD) and octadecatrienoic acid (HPOT) was also obtained by the enriched LOX activity. Four major hydroperoxy-eicosatetraenoic acid (HPETE) regioisomers, including the 8-, 9-, 12-and 15-HPETEs, were obtained from the bioconversion of arachidonic acid. Chiral studies of end products indicated varying degrees of enantio-selectivity, producing excesses in favour of the (S) stereo-isomer, for the hydroperoxide end-products resulted from the bioconversion of linoleic, linolenic and arachidonic acids.

EXTRACTION, PURIFICATION AND CHARACTERIZATION OF LIPOXYGENASE FROM CONOPHOR NUT (Tetracarpidium conophorum)

“…Kuribayash et al (2002) also reported that the Km and Vmax of LOX from Pleurotus ostreatus were 0.13 mM and 23.4 µmol/min/mg, respectively. However, soybean LOX-1 Km was 0.02 mM (Hall et al, 2004), while for canola seed (0.2 mM) (Khalyfa et al, 1990), for tomato 0.52 mM (Todd, et al, 1990), for a land plant Phaseolus vulgaris L. it was 1.4 mM (Sicilia, et al, 2005), and 2.8 mM for broad bean (Al-Obaidy and Siddioi,1981). Polyacrylamide gel electrophoresis in the presence of a surfactant SDS produced a single protein band as represented on Figure 9.…”