Screening of Yeasts Other than Saccharomyces for Amino acid Decarboxylation

Abstract

This study is aimed at screening non-Saccharomyces for amino acids decarboxylation potentials. The yeasts were isolated from banana fruit and honey purchased from markets in Rivers State. The isolation and molecular identification of yeast isolates were according to standard microbiological procedures. A plate assay method for amino acid decarboxylation (biogenic amine production) screening was used. Wild Non-Saccharomyces yeast (NSY) were identified as Candida tropicalis Pe 1 (B7), Candida tropicalis WC65-1 (B10), Candida tropicalis WC57 (H4), Clavispora lusitaniae WM03 (H7), and a Commercial Wine yeast (CY) identified as Candida tropicalis zhuan4 (CY). The NSYs and CY were biogenic amine producers, from L-histidine and glutamic acid; strain variability from glycine, proline, glutamine, and asparagine decarboxylation; while L-arginine, lysine, tyrosine, cysteine, leucine, and phenylalanine were not decarboxylated at a concentration of 0.1 %. The increase in amino acid concentration influenced the number of amino acids decarboxylated - phenylalanine and leucine; L-histidine, glycine, asparagine and glutamic acid were decarboxylated by wild NSY and CY, while the strain variability of phenylalanine, proline, leucine and glutamic acid decarboxylation. The amino acids L-arginine, lysine, tyrosine, and cysteine were not decarboxylated. In terms of the concentration of amino acids, L-histidine and glutamic acid were decarboxylated and arginine, lysine, tyrosine, and cysteine were not decarboxylated by wild NSY isolates and CY. The Chi-square Test and Kendall’s Test of concordance suggest that there is no association between the amino acid concentrations (0.1 and 1 %) and biogenic amine production (P-value > 0.05). The wild NSY and CY are biogenic amine-producers, and the increase in amino acid concentration influences biogenic amine production concerning some amino acids.