Genotypic and Phenotypic Diversity ofKluyveromyces marxianusIsolates Obtained from the Elaboration Process of Two Traditional Mexican Alcoholic Beverages Derived from Agave: Pulque and Henequen (Agave fourcroydes) Mezcal

Abstract

Seven Kluyveromyces marxianus isolates from the elaboration process of pulque and henequen mezcal were characterized. The isolates were identified based on the sequences of the D1/D2 domain of the 26S rRNA gene and the internal transcribed spacer (ITS-5.8S) region. Genetic differences were found between pulque and henequen mezcal isolates and within henequen mezcal isolates, as shown by different branching patterns in the ITS-5.8S phylogenetic tree and (GTG)5 microsatellite profiles, suggesting that substrate and process selective conditions may originate different K. marxianus populations. All the isolates fermented and assimilated inulin and lactose and some henequen isolates could also assimilate xylose and cellobiose. Henequen isolates were more thermotolerant than pulque isolates which in contrast presented more tolerance to the cell wall-disturbing agent calcofluor white (CFW) suggesting that they had a different cell wall structure. Additionally, depending on their origin, the isolates presented different maximum specific growth rates (umax) patterns at different temperatures. Concerning tolerance to stress factors relevant for lignocellulosic hydrolysates fermentation, tolerance limits were lower at 42 than 30°C except for glucose and furfural. Pulque isolates were less tolerant to ethanol, NaCl, and Cd. Finally, all the isolates could produce ethanol by simultaneous saccharification and fermentation (SSF) of a corncob hydrolysate under laboratory conditions at 42°C.