Ethanol Fermentation With Kluyveromyces Marxianus At High Temperature

In this paper, the Kluyveromyces marxianus HY32 was mutanted by the irradiation of UV(ultraviolet lights) and the red colony screened out with TTC(2,3,5-Triphenyltetrazolium chloride), the purpose was to screen out the mutants with higher ethanol production. But we can’t obtained a good performed mutants. The darker the colour, the higher the ethanol production, in theory. Many deep colored mutants was screened out, but the production of ethanol was lower than the parent Kluyveromyces marxianus HY32. This result indicated that the coloration of TTC have no positive correlation with ethanol production.Kluyveromyces marxianus HY32 have an obvious advantage over Saccharomyces cerevisiae yeast TRADY. The ethanol production of Saccharomyces cerevisiae yeast TRADY was 7.463%(v/v) at 37 ℃, Kluyveromyces marxianus HY32 was 5.979%(v/v).The fermentation temperature increased to 40℃ and 42℃, the ethanol production with Saccharomyces cerevisiae TRADY were decreased to3.689%(v/v) and 3.468%(v/v), yet Kluyveromyces marxianus HY32 were 6.434%(v/v)and 5.867%(v/v) at 40 ℃ and 42 ℃, respectively. Kluyveromyces marxianus HY32 performed a good thermostability, yet the Saccharomyces cerevisiae TRADY have not.The ethanol production of Kluyveromyces marxianus HY32 higher than other Kluyveromyces marxianus. The comparison of the ethanol production between Kluyveromyces marxianus HY32 and the two other reference strains(Kluyveromyces marxianus32920; Kluyveromyces marxianus2.1549). The ethanol production of Kluyveromyces marxianus HY32 was 5.626%(v/v), Kluyveromyces marxianus32920 was 3.247%(v/v); Kluyveromyces marxianus2.1549 was 5.019%(v/v), respectively.In terms of the excellent fermentation performance, Kluyveromyces marxianus HY32 was used to ferment with cassava, and the fermentation process was optimized.The optimum fermentation conditions were obtained: material-water ratio is 1:5,fermentation time is 96 h, inoculation is 11%, fermentation temperature is 40℃,liquefaction time is 1h, liquefaction temperature is 95℃, amylase loading is20U/gstarch, glucoamalase loading is 150U/g starch, ammonium sulfate is 6g/L,initial pH is 5.0. With the optimum fermentation conditions, ethanol production is8.903%(v/v).The steam exploded corn stover was used to ferment by Kluyveromyces marxianus HY32. The effect of fermentation temperature, solid loading, celluloseloading, fermentation time, enzymolysis time and fermentation time, dilution were studied. The optimal fermentation condition and ethanol production were fermentation temperature 45 ℃, 2.884%(v/v); solid loading 30%, 4.290%(v/v);cellulose loading 30 iu/g, 3.688%(v/v); fermentation time 48 h, 3.722%(v/v);enzymolysis time 0 h(Simultaneous saccharification and fermentation), 3.946%(v/v);dilution 70%, 4.009%(v/v); respectively.There are many compounds in steam exploded corn stover, such as acetic acid,furfural. The compounds may have a bad effect on fermentation. The comparison of the ethanol production between Kluyveromyces marxianus HY32 and Issatchenkia Orientalis Z1 were studied. Kluyveromyces marxianus HY32 fermented at 45℃,Issatchenkia Orientalis Z1 fermented at 40℃, the mix(1:1) fermented at 45℃. After120 h fermentation, the ethanol production of Kluyveromyces marxianus HY32,Issatchenkia Orientalis Z1, the mixed(1:1) were 3.569%(v/v), 3.497%(v/v),3.235%(v/v), respectively. In terms of the ethanol production, Kluyveromyces marxianus HY32 slightly higher than Issatchenkia Orientalis Z1.To further improve the ethanol production, the corn stover were concentrated to149.125 g/L reducing sugar with concentration method. After 96 h fermentation, the ethanol production of the liquid and concentrate were 3.711%(v/v), 5.954%(v/v),respectively. This indicates the concentration is benefit for improving ethanol production.