Chirakarn Muangnapoh

Solvent Extraction of Biologically Derived 1,3-Propanediol with Ethyl Acetate and Ethanol Cosolvent

This study examined the use of ethyl acetate and its mixture with ethanol as cosolvent for the extraction of biologically derived 1,3-propanediol (1,3-PDO) from a fermentional process. Experimental results on extraction of the fermentation model mixture revealed that ethyl acetate was a suitable solvent, having the distribution coefficient of 1,3-PDO of 0.22 at 303.15 K. The temperature (303.15 to 323.15 K) was found not to have a significant effect on the distribution coefficient. On the other hand, the addition of glycerol into the feed aqueous stream (at the concentrations of 4, 8, 12 g/L) was found to increase the distribution coefficient of 1,3-PDOs, however, the compound selectivity decreased. When ethanol was used as a cosolvent at the volume ratio of ethyl acetate to ethanol of 90:10, the distribution coefficient increased from 0.22 to 0.31 at 303.15 K. This decreased the number of theoretical stages (NTS) required to achieve 90% recovery of 1,3-PDO from the aqueous phase from 3 to 2 stages at the solvent to feed (S/F) ratio of 9. In addition, the extraction results with actual fermentation broth at 303.15 K indicated that the use of ethanol cosolvent could improve the distribution coefficient of 1,3 PDO from 0.14 to 0.20.

Isolation and Rheological Properties of Tamarind Seed Polysaccharide from Tamarind Kernel Powder Using Protease Enzyme and High-Intensity Ultrasound

The effectiveness of using protease and combinations of protease and high-intensity ultrasound for high-purity, high-yield tamarind seed polysaccharide (TSP) production was investigated. Tamarind kernel powder (TKP) suspension was treated with protease alone at 0.16, 0.48, and 0.80 units/mL and with protease-ultrasound combinations over 3 different orders of sequence (before, simultaneous with, and after protease digestion) using combinations of 0.48 units/mL protease and high-intensity ultrasound at 25% and 50% amplitude for 15 and 30 min. The long protease digestion time could produce high-purity isolated TSP, but the polysaccharide yields were lower. The polysaccharide purity and yield were highly improved, even at a shorter protease digestion time, when the protease treatment was combined with high-intensity ultrasound. The increased amplitude level and sonication time decreased the average molecular weight of the polysaccharide. The rheological properties of the TKP and the isolated TSP, from nondestructive oscillatory measurements, demonstrated that the latter present a viscoelastic solution. The decreasing of protein content resulted in better elasticity of the solution. The power law model could be used to fit the down curve between shear rate and shear stress data. The consistency coefficient (K) increased while the flow behavior index decreased with the increased purity of the polysaccharide as a result of increasing increased digestion time, enzyme concentration, sonication power, and sonication time.

Use of hemicellulase in sequence with hydrogen peroxide and laccase for improvement of teak veneer surface color

Teak veneer was treated with a commercial hemicellulase from Thermomyces lanuginosus in sequence with hydrogen peroxide or a hydrogen peroxide-laccase mixture to improve the veneer surface color and at the same time to reduce the necessary amount of hydrogen peroxide. The removal of a small portion of hemicellulose from the teak veneer surface could be carried out after treatment with the hemicellulase preparation as 0.05 xylanase unit/ml for 30 min. The veneer samples immediately after the hemicellulase treatment were subjected to the designated concentration of hydrogen peroxide or hydrogen peroxide-laccase mixture at 60°C at pH 6.5 for 4 h. The changes in veneer color were measured by using imaging technology as percentage change in gray scale. A treatment combination of hemicellulase containing xylanase, hydrogen peroxide, and laccase yielded a color improvement close to that achieved using 20% hydrogen peroxide. The results showed that hemicellulase pretreatment could improve the bleachability of teak veneer surfaces treated with hydrogen peroxide or hydrogen peroxide-laccase mixture.

ENHANCEMENT OF AMINO ACID PRODUCTION BY TWO-STEP AUTOLYSIS OF SPENT BREWER'S YEAST

A two-step autolysis process was proposed to enhance amino acid production from spent brewers yeast. The technique was developed based on comparative study of the dynamics of production and release of proteins and amino acids during the autolysis of a concentrated suspension (22 wt.%) and a dilute yeast cell suspension (11.25 wt.%). The results suggest that, in the concentrated yeast suspension, proteins are more effectively broken down into amino acids, but the product release rate was lower due to a lower concentration gradient across the cell membrane. Thus, a two-step process, in which a high protein conversion occurred in a concentrated cell suspension during the first 13 h period, followed by a 26 h autolysis process within a dilute cell suspension, provided a higher overall yield of amino acids compared than the single-step process. The two-step process was found to result in a 25% higher amino acid yield with a weight fraction increase from 0.4 to 0.5 g/g dry wt. Other than these findings, the effect of adding NaCl to the suspension during autolysis was also investigated. It was found that, for the autolysis conditions employed in this study, the addition of NaCl did not significantly affect the production of protein but inhibited the production of amino acids.