Thirty-seven basidiomycetous yeasts belonging to 30 species of seven genera were grown on media containing l-cysteine or l-methionine as sole nitrogen sources with the objective of evaluating volatile organic sulfur compound (VOSC) production. The headspace of yeast cultures was analyzed by the solid-phase microextraction (SPME) sampling method, and volatile compounds were quantified and identified by GC-MS techniques. Ten strains assimilating L-methionine produced the following VOSCs: 3-(methylthio)-1-propanol, methanethiol, S-methyl thioacetate, dimethyl disulfide, dimethyl trisulfide, allyl methyl sulphide and 4,5-dihydro-3(2H)-thiophenone. Production was <1 mgl(-1) except for 3-(methylthio)-1-propanol of which between 40 and 400 mgl(-1) was synthesized. Higher alcohols (isobutyl alcohol, isoamyl alcohol and active amyl alcohol) and esters (ethyl acetate, ethyl propionate, n-propyl acetate, isobutyl acetate, n-propyl propionate, n-butyl acetate, isoamyl acetate, amyl acetate, isoamyl propionate, amyl propionate and 2-phenylmethyl acetate) were also sporadically produced. This is the first report of VOSCs production by basidiomycetous yeasts. Consequently, basidiomycetous yeasts may be considered an interesting new group of microbial VOSCs producers for the flavor industry.
Studying the genetic control of molecular, anatomical and/or morphological phenotypes in model organisms is a powerful tool in the functional analysis of a gene. The goal of our research is to develop algorithms that discover phenotypes of behavior in model organisms, which may identify, categorize, and quantify these phenotypes under conditions of minimal a priori information. Starting from a non-invasive video monitoring of a model organism, we propose an eigen-decomposition of the organism's behavior captured in video. Traditional clustering techniques in space, time, and frequency can utilize this decomposition to characterize the categorical behaviors of an animal, and for an analysis of the behavioral repertoire. This supplies a quantified analysis of behavior with minimal assumptions, a crucial first step in the genetic analysis of behavior.
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