Synthesis and characterization of bacterial cellulose/alginate blend membranes

Bacterial cellulose and alginate in an aqueous NaOH/urea solution were used as substrate materials for the fabrication of a novel blend membrane. The blend solution was cast onto a Teflon plate, coagulated in a 5 wt % CaCl₂ aqueous solution, and then treated with a 1% HCl solution. Supercritical carbon dioxide drying was then applied for the formation of a nanoporous structure. The physical properties and morphology of the regenerated bacterial cellulose and blend membranes were characterized. The blend membrane with 80% bacterial cellulose/20 wt % alginate displayed a homogeneous structure and exhibited a better water adsorption capacity and water vapor transmission rate. However, the tensile strength and elongation at break of the film with a thickness of 0.09 mm slightly decreased to 3.38 MPa and 31.60%, respectively. The average pore size of the blend membrane was 10.60 Å with a 19.50 m²/g surface area. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ethanol production by repeated batch and continuous fermentations of blackstrap molasses using immobilized yeast cells on thin-shell silk cocoons

A thin-shell silk cocoon (TSC), a residual from the silk industry, is used as a support material for the immobilization of Saccharomyces cerevisiae M30 in ethanol fermentation because of its properties such as high mechanical strength, light weight, biocompatibility and high surface area. In batch fermentation with blackstrap molasses as the main fermentation substrate, an optimal ethanol concentration of 98.6 g/L was obtained using a TSC-immobilized cell system at an initial reducing sugar concentration of 240 g/L. The ethanol concentration produced by the immobilized cells was 11.5% higher than that produced by the free cells. Ethanol production in five-cycle repeated batch fermentation demonstrated the enhanced stability of the immobilized yeast cells. Under continuous fermentation in a packed-bed reactor, a maximum ethanol productivity of 19.0 g/(L h) with an ethanol concentration of 52.8 g/L was observed at a 0.36 h⁻¹ dilution rate.     

Alginate-loofa as carrier matrix for ethanol production

An alginate-loofa matrix was developed as a cell carrier for ethanol fermentation owing to its porous structure and strong fibrous nature. The matrix was effective for cell immobilization and had good mechanical strength and stability for long-term use. After a storage period of 4 months, yeast cells remained firmly immobilized and active.     

Hydrolysis of cassava starch by co-immobilized multi-microorganisms of Loog-Pang (Thai rice cake starter) for ethanol fermentation

Food Science and Biotechnology - Loog-Pang (Thai rice cake starter) is an effective and inexpensive microbial source for the hydrolysis of cassava starch to glucose. A process for hydrolysis of...     

Influences of operating conditions on biocatalytic activity and reusability of Novozym 435 for esterification of free fatty acids with short-chain alcohols:A case study of palm fatty acid distillate

In the present study, the effects of operating conditions on biocatalytic activity and stability of Novozym 435 for repeated-batch biodiesel production from free fatty acid (FFA) were investigated. Thermal deactivation caused by increased operating temperature from 45 to 50 °C could seriously affect the reusability of Novozym 435. The deactivation of Novozym 435 during the esterification of oleic acid with ethanol tended to be stronger than that in the system with methanol. Under the optimal conditions, considering both biocatalytic activity and stability of the enzyme, Novozym 435 could be reused for 13 cycles for biodiesel productions from oleic acid and absolute alcohols (methanol and ethanol) with FFA conversions of at least 90%. The presence of 4%–5%water in ethanol significantly affected the reusability of Novozym 435. Changes in the surface morphology of Novozym 435 during the esterification with various conditions were observed. It was revealed that the reduc-tion in catalytic activity was related to the swel ing degree of the catalyst surface. Additionally, biodiesel produc-tion from low cost renewable feedstocks, such as palm fatty acid distillate (PFAD) and 95%ethanol was examined. The esterification of PFAD with 95%ethanol catalyzed by Novozym 435 in 10-repeated batch operation showed the similar results in FFA conversion as compared to those using oleic acid. Novozym 435 remained active and could maintain 97.6%of its initial conversion after being used for 10 batches.     

A comparison of three different dihydroartemisinin formulations for the treatment of acute uncomplicated falciparum malaria in Thailand

This study was aimed at assessing the response to electrochemotherapy with cisplatin of cutaneous tumour nodules in patients with malignant melanoma, squamous cell carcinoma and basal cell carcinoma. In 4 patients, 30 tumour nodules of different sizes were treated; five without treatment, one with electric pulses, five with cisplatin injected intratumorally and 19 with electrochemotherapy, i.e. intratumoral administration of cisplatin followed by delivery of electric pulses to the tumour nodule. After 4 weeks, a complete response (CR) in all 19 electrochemotherapy treated nodules was obtained. All electrochemotherapy treated nodules remained in CR (range 7-11 months), regardless of histological type, except for the metastasis of a squamous cell carcinoma that progressed after 9 months. CR was also obtained in two of five tumour nodules treated with cisplatin intratumorally, but the other three nodules progressed within 3-7 months. Exposure of the tumour nodule to electric pulses without cisplatin treatment had no effect on tumour growth. Electrochemotherapy was well tolerated by all patients and a good cosmetic effect was obtained, with only minimal scarring and a slight depigmentation of the skin. Electrochemotherapy with cisplatin has proved to be effective in patients with cutaneous tumour nodules. Furthermore, electrochemotherapy is easy to perform and can be carried out on an out-patient basis.     

Novel nanoporous membranes from regenerated bacterial cellulose

Bacterial cellulose (BC) in an NaOH/urea aqueous solution was used as a substrate material for thefabrication of a novel regenerated cellulose membrane. The dissolution of BC involved swelling BC in a 4 wt % NaOH/3 wt % urea solution followed by a freeze–thaw process. The BC solution was cast onto a Teflon plate, coagulated in a 5 wt % CaCl₂ aqueous solution, and then treated with a 1 wt % HCl solution. Supercritical carbon dioxide drying was then applied to the formation of a nanoporous structure. The physical properties and morphology of the regenerated bacterial cellulose (RBC) films were characterized. The tensile strength, elongation at break, and water absorption of the RBC membranes were 4.32 MPa, 35.20%, and 49.67%, respectively. The average pore size of the RBC membrane was 1.26 nm with a 17.57 m²/g surface area. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biosynthesis and characterization of bacteria cellulose–alginate film

A novel polysaccharide membrane containing alginate in bacterial cellulose matrix was synthesized by Acetobacter xylinum under static conditions using a culture medium supplementation with sodium alginate. By increasing alginate content, the bacterial cellulose–alginate (BCA) membrane was more hydrophilic and the film structure became denser with the smaller average pore size. Scanning electron microscope images displayed the deposits of alginate gel on the surfaces of the multilayer cellulose film. The declines in the tensile strength, the Young's modulus, and the elongation at break of the BCA membrane were dependent on the degree of alginate supplement. The BCA membrane showed higher water absorption capacity. The addition of alginate slightly affected the water vapor transmission rate but remarkably decreased the oxygen transmission rate of the membrane. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

High-temperature ethanol fermentation by immobilized coculture of Kluyveromyces marxianus and Saccharomyces cerevisiae

Suspended and immobilized cocultures of the thermotolerant yeast, Kluyveromyces marxianus DMKU 3-1042 and the mesophilic flocculent yeast, Saccharomyces cerevisiae M30 were studied for their abilities to improve production and stability of ethanol fermentation. Sugarcane juice and blackstrap molasses, at initial sugar concentrations of 220 g/L, were used as carbon sources. The results indicated that the coculture system could improve ethanol production from both sugarcane juice and blackstrap molasses when the operating temperature ranged between 33 °C and 45 °C. High temperature tolerances were achieved when the coculture was immobilized. The immobilized coculture was more effective in high-temperature ethanol fermentation than the suspended cultures. The coculture immobilized on thin-shell silk cocoon and fermented at 37 °C and 40 °C generated maximal ethanol concentrations of 81.4 and 77.3 g/L, respectively, which were 5.9-8.7% and 16.8-39.0% higher than those of the suspended cultures, respectively.