Doxycycline and monosodium glutamate (MSG) loaded chitosan (CHI)/polylactic acid (PLA)/polycaprolactone (PCL) blend film was studied as a model device to deliver drug to targeted human organ which in this case was the skin with opened wound. The CHI/PLA/PCL blend film containing 60 % CHI, 28 % PLA, and 12 % PCL exhibited the good properties for making the dressing device. It was observed that doxycycline/MSG loaded CHI/PLA/PCL blend film could rapidly deliver both doxycycline and MSG at the high release percentage approaching 100 % loaded. MSG accelerated blood clotting and fibrin formation; thus, it exhibited the good hemostatic activity. The antibacterial activity of doxycycline loaded CHI/PLA/PCL blend film against Staphylococcus aureus and Escherichia coli as model bacteria was investigated. Doxycycline release played the crucial role in bacterial inhibition as observed from the lowest bacterial cell dry weight observed when compared with the control bacterial culture or the bacterial cultures with the presence of other films studied.

The use of biopolymers as bioadhesives for human tissue is becoming a preferred alternative to suturing due to their superior adhesive, biocompatible, and biodegradable properties. In this work, low molecular weight poly(L-lactide-co--caprolactone) (P(LA-co-CL) was synthesized to achieve the glass transition temperature (T g ) of the copolymer at ambient temperature so that during application on the skin, the copolymer when combined with chitosan (CHI) into the CHI/P(LA-co-CL) film could provide the strong support at the injury site. Using alcohols with different numbers of hydroxyl groups as the co-initiator in polymerization provided the distinctive characteristics of copolymers. Among all copolymers synthesized, P(LA-co-CL) copolymer using pentaerythritol as the co-initiator when combined with CHI at the ratio of copolymer/CHI at 70/30 yielded the good film properties in tissue adhesion and tetracycline hydrochloride release.

Lactic acid has long been widely used in many applications. Currently, the worldwide market is increasing due to the discovery of biodegradable polylactic acid. In this work, L-lactic acid separations from filamentous fungal fermentation broth using ion-exchange chromatography and in-house electrodialysis, were studied and compared. Dowex Marathon WBA was used for the lactic acid separation. The adsorption equilibrium followed a Langmuir isotherm. The optimal conditions for lactic acid adsorption in a fixed-bed column were at pH 6.0, and 0.8 mL/min and elution by a mixture of 1.0 M sulfuric acid and 1.0 M phosphoric acid in a ratio of 30:70 at 0.3 mL/min. The final lactic acid recovery was 76 % with 90 % purity. A laboratory scale in-house electrodialysis apparatus was constructed with an effective membrane area of 2.925 · 10 -3 m 2 . The effects of feeding solution concentration, flow rate, pH of the fermentation broth, and applicable voltage were studied. Under the optimal conditions, lactic acid recovery was 92 % with 100 % purity and a specific energy consumption of 0.6122 kWh/kg.

Ethanol was found as the major by-product in lactate fermentation by Rhizopus oryzae. Several methods have been conducted in order to limit ethanol formation, thus increasing the lactate yield. The direct way to suppress ethanol production can be done by inhibition of the responsible enzymes in the related pathway. Pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) are responsible for ethanol production in R. oryzae. Shunting the ethanol production pathway by targeting at PDC was attempted in this study. Three compounds including 4-methylpyrazole, glyoxylic acid, and 3-hydroxypyruvate with the in vitro reversible inhibitory effect on PDC were selected from the literature and were used to regulate the living cell of R. oryzae during the fermentation. The results show that 0.1 mM 4-methylpyrazole of which the structure resembled a thiazolium ring in thiamine diphosphate, PDC cofactor, and 1.0 μm 3-hydroxypyruvate, pyruvate analog, effectively hampered ethanol production. Further observation on the enzyme expression indicated that these two regulators not only targeted PDC but also caused changes in ADH and lactate dehydrogenase (LDH) activities. This was perhaps due to the living cell of R. oryzae that responded to the presence of the regulators to balance the pyruvate flux and subsequently maintain its metabolic activities.

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