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Author: search.filters.author.Vichitraka, Assanee

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    Increasing the acetification rate of Acetobacter aceti adsorbed on luffa sponge using recycle of incremental oxygenated medium
    (2020-03-01)
    Krusong, Warawut
    ;
    Vichitraka, Assanee
    ;
    Sriphochanart, Wiramsri
    ;
    Pornpukdeewattana, Soisuda
    Speeding up the production of vinegar from rice wine by acetification, using a packed-bed bioreactor with a luffa sponge matrix (LSM) as adsorption carrier of acetic acid bacteria (AAB), and the effect of oxygenation of the recycled medium were investigated. The 0.06 L/min recycle of medium resulted in a high oxygen-transfer coefficient, while optimal dissolved oxygen (DO) of the medium maximized planktonic AAB cell growth with no contamination due to high acid in an external reservoir without LSM. The highest acetification rate (ETA) of 2.857 ± 0.1 g/L/day was achieved with DO 3.5–4.5 ppm at 35 ± 1 °C. To increase ETA, the optimized oxygenated medium was externally supplied and recycled at the ratio of 0.1. Therefore, acetification was conducted in both the bioreactor and reservoir resulting in an increased ETA (6 ± 0.2 g/L/day). This also aligned with the highest system AAB biomass (confirmed by scanning electron microscopy). Under the recycled oxygenated medium supply consistently high biotransformation yields (average 77.3%) were observed over nine sequential cycles. Meanwhile, an average ETA of 6.3 ± 0.2 g/L/day was obtained. This method can have practical applications in improving the efficiency and speeding up small-scale vinegar production.
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    Inhibitory impact of vapor-phase ethanol on conidia germination and mycelial growth of Aspergillus fumigatus on bread
    (2019-01-01)
    Krusong, Warawut
    ;
    Pothimon, Ruttipron
    ;
    Vichitraka, Assanee
    Mold contaminated on bread sold in local market was isolated and identified as Aspergillus fumigatus. Then, the bio-control of ethanol on A. fumigatus for significantly reducing consumer health risk was investigated. Susceptibility of the mold to evaporated vapor-phase ethanol (EVE) was examined in vitro. Complete elimination of viable spore and inhibition growth spread on Potato Dextrose Agar at 30 ± 2 °C of were found with exposure for 15 min to EVE (10.80 ± 0.3 mmol/L). The effect of EVE on the susceptibility of artificial inoculated A. fumigatus on bread were further examined. While exposure to EVE affected the survival conidia, the degree of reduction depended on the inoculation level. Complete reduction was achieved for the low inoculation level (2.08 ± 0.04 log conidia/g) by EVE (60 min exposure, 19.27 ± 0.3 mmol/L) but susceptibility was reduced with the high inoculation level (5.4 ± 0.06 log conidia/g). Simultaneously, total aflatoxin production decreased, as EVE exposure increased. Scanning electron microscope images of inoculated bread, confirm the effects of EVE in reducing levels of viable conidia. Hence, EVE is shown to be an effective bio-fumigant for A. fumigatus mycelial growth and aflatoxin formation on bread, so effectively reducing the potential for consumer health risks due to this widespread fungus.