Charin Techapun

Thermostable and alkaline-tolerant cellulase-free xylanase produced by thermotolerant Streptomyces sp. Ab106.

Cellulase-free xylanase was produced by Streptomyces sp. Ab106 using cane bagasse as the substrate at 55 degrees C. Its maximum activity was 13 IU without cellulase and mannanase activities. Its profiles were investigated. Its optimum temperature and pH were 60 degrees C and 6.0, respectively. More than 70% of its activity was remained at 60 degrees C at pH 9. This enzyme was quite stable and exhibited an active of more than 70% for 144 h at 60 degrees C, and of more than 80% for 144 h at 40 degrees C, pH 9. This thermo-tolerant and alkaline-tolerant xylanase can be used in the pulp bleaching process.

Optimization of aeration and agitation rates to improve cellulase-free xylanase production by thermotolerant Streptomyces sp. Ab106 and repeated fed-batch cultivation using agricultural waste

Thermostable cellulase-free xylanase was produced by Streptomyces sp. Ab106 using agricultural waste, sugar cane bagasse, as the substrate at 50 degrees C and pH 7.0. The central composite face-centered experimental design was applied to evaluate the optimal agitation and aeration rates in a 5-l fermentor. The highest activity (16.0+/-0.5 IU/ml) was obtained at an aeration rate of 1 vvm and an agitation rate of 150 rpm (k(L)a = 351 h(-1)). Using the repeated fed-batch cultivation technique, the maximum xylanase activity of 32+/-1 IU/ml was obtained during the second cycle of repeated fed-batch culture.

Production of a cellulase-free xylanase from agricultural waste materials by a thermotolerant Streptomyces sp.

Abstract1444 microorganisms were isolated from soil samples from the northern Thai and screened at 55 °C by using basal medium supplemented with 1% carboxymethyl cellulose as a sole carbon source. One isolate, Streptomyces Ab106, had a high activity of a cellulase-free xylanase also without mannanase activity. The maximum cellulase-free xylanase activities of 3.5, 3.3, 3.1 and 2.7 IU were after growth of the organism with 1% (w/v) corn hull, corncob, bagasse and oat spelt xylan, respectively, at 55 °C for 6 days, respectively. The activity was more than 5 times higher than that at 35 °C.

Optimization of cellulase-free xylanase production by thermophilic streptomyces thermovulgaris TISTR1948 through Plackett-Burman and response surface methodological approaches

Cellulase-free xylanase production by thermophilic Streptomyces thermovulgaris TISTR1948 was cultivated in a basal medium with rice straw as sole source of carbon and as an inducible substrate. Variable medium components were selected in accordance with the Plackett-Burman experimental design. The optimization conditions of physical factors (pH and temperature levels) were then combined in further studies through the response surface methodology approach. Only two significant components, rice straw and yeast extract, were chosen for the optimization studies. A second-order quadratic model was constructed by central composite design (CCD). The model revealed that both pH and temperature levels were significant, and were dependent on xylanase production. Under these experimental designs, the xylanase yield increased from 51.11 to 274.49 U/mL (3,400 to 10,000 U/g of rice straw) or about 537% higher than an unoptimized basal medium. The optimum conditions to achieve maximum yield of xylanase were 27.45 g/L of rice straw and 5.42 g/L of yeast extract under relatively neutral conditions of pH 7.11, 50.03 °C, and a incubation period.

Production of cellulase-free xylanase by a thermotolerant Streptomyces sp. grown on agricultural waste and media optimization using mixture design and Plackett–Burman experimental design methods

Cellulase-free xylanase was produced by Streptomyces sp. Ab106 on finely ground cane bagasse at 55 °C. The optimal medium composition was developed by applying the mixture design and linear mathematical program, and evaluated using the Plackett–Burman experimental design. The best composition of basal medium was found by using the mixture design method. The highest xylanase activity, 10.6 IU, was obtained after 6 days of fermentation in shaked flask at 100 rpm, 55 °C, pH 7. Both experimental designs showed that trace elements induced xylanase production. With fermentation in a 5-l fermenter, xylanase activity of 12.5 IU was achieved.

Production of xylooligosaccharides from corncob using a crude thermostable endo-xylanase from Streptomyces thermovulgaris TISTR1948 and prebiotic properties

Production of xylooligosaccharides (XOs) from corncob using the thermostable endo-xylanase from Streptomyces thermovulgaris TISTR1948 was investigated using KOH pretreatment, followed by enzymatic hydrolysis. The optimal reaction time for production of XOs was 12 h, after which xylobiose comprised a majority of products, and a low xylose content was observed. The optimal conditions for production of XOs were studied using a central composite design. At an enzyme concentration of 129.43 U/g of substrate, 53.80°C, and pH 6.17, the yield of XOs reached 162.97 mg/g of substrate or 752.15 mg/g of hemicellulose in KOH-pretreated corncob. The prebiotic properties of XOs derived from corncob were also investigated using in vitro fermentation of those XOs with the known probiotic strains Lactobacillus casei TISTR1463, L. lactis TISTR1464, and L. plantarum TISTR1465. XOs derived from corncob were comparable to commercial XOs for an ability to enhance the growth of the specified probiotic lactobacilli.

Optimization of Exopolysaccharide Overproduction by Lactobacillus confusus in Solid State Fermentation under High Salinity Stress

It is believed that high concentrations of sodium chloride (NaCl) suppress the biosynthesis of exopolysaccharide (EPS) in lactic acid bacteria (LAB). Nevertheless, overproduction of EPSs due to high salinity stress in solid state fermentation performed on an agar surface was demonstrated in this study using a response surface methodology via a central composite design (CCD). Under optimized conditions with NaCl 4.97% and sucrose 136.5 g/L at 40.79 h of incubation, the EPS yield was 259% (86.36 g/L of EPS), higher than the maximum yield produced with the modified MRS medium containing only 120 g/L of sucrose without NaCl (33.4 g/L of EPS). Biosynthesis of EPS by Lactobacillus confusus TISTR 1498 was independent of biomass production. Our results indicated that high salinity stress can enhance EPS production in solid state fermentation.

Reactive blending of thermoplastic starch and polyethylene-graft-maleic anhydride with chitosan as compatibilizer.

Cassava starch was melt-blended with glycerol (70/30wt%/wt%) at 140°C to prepare thermoplastic starch (TPS). Chitosan (CTS) was premixed with starch and glycerol, in acidified water (lactic acid 2wt%), at 1, 5 and 10wt%/wt%. TPS/CTS was then melt-blended (160°C) with polyethylene-graft-maleic anhydride (PE-MAH). Phase determination and scanning electron microscopy indicated TPS/PE-MAH/CTS had a co-continuous morphology and CTS-induced phase inversion to give dispersed PE-MAH particles in a TPS matrix. Tensile strength at break and elongation, melt viscosity, fracture toughness and water contact angle of TPS/PE-MAH were improved by CTS incorporation. TPS/PE-MAH/CTS blends decreased the melting temperature of TPS and PE-MAH compared to the neat polymers. FTIR confirmed a reaction had occurred between amino groups (NH2) of CTS and the MAH groups of PE-MAH. This reaction and the enhanced miscibility between TPS and CTS improved the mechanical properties of the TPS/PE-MAH/CTS blend, particularly at 5wt%/wt% CTS.

Characterization of the native form and the carboxy‐terminally truncated halotolerant form of α‐amylases from Bacillus subtilis strain FP‐133

Two amylases, amylase I and amylase II from Bacillus subtilis strain FP‐133, were purified to homogeneity and characterized. Their stabilities toward temperature, pH, and organic solvents, and their substrate specificities toward polysaccharides and oligosaccharides were similar. Under moderately high salt conditions, both amylases were more stable than commercial B. licheniformis amylase, and amylase I retained higher amylase activity than amylase II. The N‐terminal amino acid sequence, genomic southern blot analysis, and MALDI‐TOFF‐MS analysis indicated that the halotolerant amylase I was produced by limited carboxy‐terminal truncation of the amylase II peptide. The deduced amino acid sequence of amylase II was >95% identical to that of previously reported B. subtilis α‐amylases, but their carboxy‐terminal truncation points differed. Three recombinant amylases — full‐length amylase corresponding to amylase II, an artificially truncated amylase corresponding to amylase I, and an amylase with a larger artificial C‐terminal truncation — were expressed in B. subtilis. The artificially truncated recombinant amylases had the same high amylase activity as amylase I under moderately high salt conditions. Sequence comparisons indicated that an increased ratio of Asp/Glu residues in the enzyme may be one factor responsible for increasing halotolerance.

Solid State Fermentation for Extracellular Polysaccharide Production by Lactobacillus confusus with Coconut Water and Sugar Cane Juice as Renewable Wastes

Extracellular polysaccharide (EPS) production by Lactobacillus confusus in liquid and solid state fermentation was carried out using coconut water and sugarcane juice as renewable wastes. High concentrations of EPS of 62 (sugarcane juice) and 18 g/l of coconut water were produced in solid state fermentation when nitrogen sources were reduced 5-fold from the original medium.