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''Secondary metabolites'' are compounds that are not essential to the life of an organism <ref>[http://en.wikipedia.org/wiki/Secondary_metabolite Wikipedia. Secondary Metabolite. Retrieved 6/2/2015.]</ref>. ''Brettanomyces'' will use a range of secondary metabolites to produce many of the fruity and funky esters, phenols, and acids that this genus of yeast has become known for. ''Brettanomyces'' has also been observed anecdotally to produce thin beer when fermented on it's own, and this has at least partially been attributed to the lack of glycerol production by ''Brettanomyces''. The lack of glycerol production has been attributed to a genetic predisposal to prefer pyruvate production over glycerol production during fermentation, and it has been speculated that this gives ''Brettanomyces'' an adaptive advantage <ref>[http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0155140 Independent Evolution of Winner Traits without Whole Genome Duplication in Dekkera Yeasts. Yi-Cheng Guo, Lin Zhang, Shao-Xing Dai, Wen-Xing Li, Jun-Juan Zheng, Gong-Hua Li, Jing-Fei Huang. 2016.]</ref><ref name="yakobson_introduction"></ref>. The major secondary metabolites of ''B. bruxellensis'' fermentation have been identified in one study as the ethyl phenols (4EP and 4EG), the alcohols isoamyl alcohol, 2-methyl-butanol, 2-ethylhexanol, phenethyl alcohol, and an ester ethyl 2-methyl butyrate. Many other compounds are considered minor secondary metabolites and are produced in varying degrees or not at all based on the strain of ''Brettanomyces'', but may still be produced in high enough concentrations to contribute to the flavor and/or aroma in beers fermented with ''Brettanomyces''. The types and amounts of flavor compounds produced by ''Brettanomyces'' cover a wide spectrum, and many factors such as species/strain, amino acid precursors, presence of oxygen, and other nutrients, play a large role in production of these compounds. In one study on ''Brettanomyces'' in wine, some strains rated as being perceived positively if the strains metabolized certain compounds slower and produced other compounds slower, indicating that the age of the fermented beverage also plays a large role in how beverages fermented with ''Brettanomyces'' are perceived <ref name="Lucy_2015" />. Some strains of ''B. bruxellensis also produce the amines cadaverine, hexylamine, phenylethylamine, putrescine and spermidine, under wine-model conditions <ref name="Agnolucci_2017" />.