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Author: search.filters.author.Krusong, WarawutSubject: search.filters.subject.Adaptation

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    Conducting High acetic acid and temperature acetification processes by Acetobacter pasteurianus UMCC 2951
    (2020-11-01)
    Pothimon, Ruttipron
    ;
    Gullo, Maria
    ;
    La China, Salvatore
    ;
    Thompson, Anthony Keith
    ;
    Krusong, Warawut
    In this study Acetobacter pasteurianus strain UMCC 2951 was tested as a microbial starter to conduct acetification processes by repeatedly cultivation cycles under high temperature acetification at 40 ± 1 °C. Acid production and acetification rate increased with repeated cultures under high temperature acetification as adaptation period increased, but were still lower than acetification at 30 ± 1 °C. However, the addition of 0.15 % calcium chloride reduced the negative effects of 40 ± 1 °C on both acid production and acetification rate compared to 30 ± 1 °C. A strong decrease in fatty acids and phosphatidylethanolamine and increases in phosphatidylcholine and phosphatidylglycerol in cell membranes were found under high acid and high temperature acetification. In addition, transmission electron microscope images reveal a more compact cell wall when calcium chloride was added to the cultivation medium. The strategy used in this study confirmed that the use of acetic acid bacteria as microbial starters could be effective also at temperature above the optimal values, when acetification processes are managed through repeated semi-continuous cycles.
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    Repeated cultures of Saccharomyces cerevisiae SC90 to tolerate inhibitors generated during cassava processing waste hydrolysis for bioethanol production
    (2019-03-01)
    Palakawong Na Ayutthaya, Pakathamon
    ;
    Charoenrat, Theppanya
    ;
    Krusong, Warawut
    ;
    Pornpukdeewattana, Soisuda
    Large amount of cassava pulp is produced as by-product of industrial tapioca production. The value-added process of this low-cost waste is to use it as a substrate for bioethanol production. However, during the pulp pretreatment by acidification combined with steam explosion, many yeast inhibitors including acetic acid, formic acid, levulinic acid, furfural and 5-hydroxymethylfurfural are generated and these compounds have negative effects on the subsequent fermentation step. Therefore, the objective of this study was to investigate whether the repeated cultures of Saccharomyces cerevisiae SC90 could alleviate this problem. To obtain the inhibitor tolerable cells, the repeated culture was performed by growing yeast cells to a specific growth rate (µ) of 0.22 h <sup>−1</sup> or higher (80% of the µ in control) and then transferring them to progressively higher concentrations of hydrolysate ranging from 20 to 100% (v/v). The results showed a tendency of longer lag phase as well as time to reach maximum cell number (t <inf>maxc</inf> ) with an increase in hydrolysate concentration. However, the repeated culture at the same hydrolysate concentration could shorten both lag period and t <inf>maxc</inf> . Interestingly, the growth and fermentation efficiency of adapted cells in 100% hydrolysate were significantly higher (p ≤ 0.05) than those of non-adapted cells by 38% and 27%, respectively.