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    Kinetic parameters of Candida tropicalis TISTR 5306 for ethanol production process using an optimal enzymatic digestion strategy of assorted grade longan solid waste powder
    (2019-11-01)
    Wattanapanom, Saengkae
    ;
    Muenseema, Jidapa
    ;
    Techapun, Charin
    ;
    Jantanasakulwong, Kittisak
    ;
    Sanguanchaipaiwong, Vorapat
    The optimal enzymatic digestion strategy for assorted grade whole fruit longan solid waste powder (WF–LSWP) to release the highest level of fermentable sugars for subsequent production of ethanol using Candida tropicalis TISTR 5306 has been reported for the first time in this study with several important fermentation kinetic parameters. WF–LSWP contained relatively low lignin content (5.79 ± 0.43 %(w/w)) with the presence of relatively high starch and pectin contents of 27.9 ± 0.86% (w/w) and 2.07 ± 0.16% (w/w), respectively. Pretreatment by alkali and saturated steam before enzymatic digestion step did not result in the improvement of overall sugars being released. The implementation of commercial enzyme mixture (amylase, glucoamylase, cellulase, and xylanase) for one step enzymatic digestion at 50°C for 48 h resulted in the statistical significantly highest (p ≤ 0.05) specific overall sugars productivity of (141 ± 1.4) × 10<sup>–4</sup> g total sugars/g WF–LSWP/digestion step/h. Cultivation of C. tropicalis TISTR 5306 in digested and concentrated WF–LSWP extract at concentration level of 90 g/l during 0 – 12 h resulted in the following statistical significantly highest (p ≤ 0.05) kinetic parameters; specific growth rate (m) of 0.097 ± 0.001 h<sup>–1</sup> and specific ethanol production rate (q<inf>P</inf>) of 0.221 ± 0.010 gP/gX/h. Dried biomass yield (Y<inf>X/S</inf>) and ethanol yield (Y<inf>P/S</inf>) based on utilized sugars of 90 g/l WF–LSWP extract at 0.180 ± 0.018 gX/gS and 0.411 ± 0.044 gP/gS, respectively, were statistical significantly highest (p ≤ 0.05) in comparison with those of 16 and 45 g/l WF–LSWP extracts.
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    Development of mathematical model for pyruvate decarboxylase deactivation kinetics by benzaldehyde with inorganic phosphate activation effect
    (2018-05-01)
    Khemacheewakul, Julaluk
    ;
    Techapun, Charin
    ;
    Kuntiya, Ampin
    ;
    Sanguanchaipaiwong, Vorapat
    ;
    Chaiyaso, Thanongsak
    The effect of phosphate concentrations at 20, 250, 500, and 1,000 mM on phenylacetylcarbinol (PAC) production, pyruvate decarboxylase (PDC) deactivation kinetics, and combination of phosphate activation effect in a mathematical model were evaluated in a biotransformation system using whole cells of Candida tropicalis TISTR 5350. This is the first report of phosphate activation effect on pyruvate decarboxylase deactivation model. The highest PAC concentration (28.6 ± 2.3 mM), average instantaneous PAC formation rate (0.57 ± 0.01 mM/min), PAC yields (0.95 ± 0.08 on benzaldehyde and 0.71 ± 0.06 on pyruvate) were achieved in 1,000 mM phosphate buffer. PDC volumetric activity of 0.52 ± 0.07 U carboligase/ml at the reaction time of 180 min was obtained. The mathematical model describing deactivation kinetics of whole cells PDC by benzaldehyde with activation effect for phosphate buffer concentration level predicted individual experimental data for all four levels of phosphate buffer relatively well with corresponding residual sum of square (RSS), mean square (MS), and correlation coefficient (R<sup>2</sup>) range of 213-1,100, 5.32-27.5, and 0.96-0.99. The activation effect of 1,000 mM phosphate buffer was evident with an average enzyme activation rate constant due to buffering species concentration level (K<inf>a</inf>) of 1.34 × 10<sup>-2</sup> % min<sup>-1</sup> which was higher than 20 mM phosphate buffer (1.48 × 10<sup>-6</sup> % min<sup>-1</sup>) by more than 9,050 times.
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    Partial purification and comparison of precipitation techniques of pyruvate decarboxylase enzyme
    (2017-01-01)
    Tangtua, Julaluk
    ;
    Techapun, Charin
    ;
    Pratanaphon, Ronachai
    ;
    Kuntiya, Ampin
    ;
    Sanguanchaipaiwong, Vorapat
    The intracellular pyruvate decarboxylase enzyme (PDC, EC 4.1.1.1) extract from Candida tropicalis TISTR 5350 was compared by two different purification methods using ammonium sulphate and acetone precipitation. The total volumetric PDC activity and percentage recovery (yield) of precipitated PDC based on 50% (v/v) cold acetone were significantly higher (1.13 ± 0.02 U/ml and 98.27 ± 2.98 %, respectively) than any other concentration levels of acetone used. Furthermore, all concentration levels of cold acetone also yielded a much higher specific PDC activity than the precipitate obtained using the 40 to 60% (w/v) ammonium sulphate saturation (0.75 ± 0.08 U/mg protein). The precipitated enzyme in buffer solutions from the 50% (v/v) acetone was subsequently freeze dried. Freeze drying of the precipitated PDC by cold acetone resulted in the specific PDC activity of 1.57 ± 0.02 U/mg protein and differed statistically (p ≤ 0.05) from the crude enzyme extract (control).