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1.
Article in English | WPRIM (Western Pacific) | ID: wpr-625759

ABSTRACT

The mannan-degrading enzymes produced by Aspergillus niger were concentrated and the activities were evaluated. The optimum pH for -mannanase, endoglucanase and -galactosidase were obtained at pH 3.5 while pH optimum for -mannosidase was occurred at pH 3.0. The -mannanase, endoglucanase, -mannosidase and -galactosidase was stable at pH 3.5 to 7, pH 3.5 to 6.5, pH 4 to 7 and pH 3.5 to 5.0, respectively. The enzymes obtained in this study were characterized and defined as acidic proteins. The -mannanases from A. niger had two optimum temperatures (at 50 °C and 60 °C) and its half-life was 6 h and 4 h at 60 °C and 70 °C, respectively. The -mannosidase, endoglucanase and -galactosidase displayed optimal activity at 70 °C, 60 °C and 50 – 60 °C, respectively. The -mannosidase had half-life of 1.5 h at 70 °C, while -galactosidase had a half-life of 2.5 h at 60 °C and endoglucanase had a half-life of 6 h at 60 °C and 45 min at 70 °C.

2.
Bioresour Technol ; 99(14): 6097-104, 2008 Sep.
Article in English | MEDLINE | ID: mdl-18243690

ABSTRACT

Lipase-catalyzed production of palm esters by alcoholysis of palm oil with oleyl alcohol in n-hexane was performed in 2L stirred-tank reactor (STR). Investigation on the performance of reactor operation was carried out in batch mode STR with single impeller mounted on the centrally located shaft. Rushton turbine (RT) impellers provide the highest reaction yield (95.8%) at lower agitation speed as compared to AL-hydrofoil (AL-H) and 2-bladed elephant ear (EE) impellers. Homogenous enzyme particles suspension was obtained at 250 rpm by using RT impeller. At higher impeller speed, the shear effect on the enzyme particles caused by agitation has decreased the reaction performance. Palm esters reaction mixture in STR follows Newtons' law due to the linear relation between the shear stress (tau) and shear rate (dupsilon/dy). High stability of Lipozyme RM IM was observed as shown by its ability to be repeatedly used to give high percentage yield (79%) of palm esters even after 15 cycles of reaction. The process was successfully scale-up to 75 L STR (50 L working volume) based on a constant impeller tip speed approach, which gave the yield of 97.2% after 5h reaction time.


Subject(s)
Esters/metabolism , Lipase/metabolism , Catalysis , Chromatography, Gas , Rheology , Viscosity
3.
Int J Food Microbiol ; 102(2): 137-42, 2005 Jul 15.
Article in English | MEDLINE | ID: mdl-15992613

ABSTRACT

This study was undertaken to optimize yeast extract, glucose, and vitamin concentrations; and also culture pH for maximizing the growth of a probiotic bacterium, Lactobacillus rhamnosus, and to assess the effects of these factors by using response surface methodology. A central composite design was used as an experimental design for the allocation of treatment combinations. A polynomial regression model with cubic and quartic terms was used for analysis of the experimental data. It was found that the effects involving yeast extract, glucose, vitamins and pH on the growth of L. rhamnosus were significant, and the strongest effect was given by the yeast extract concentration. Estimated optimum conditions of the factors for the growth of L. rhamnosus are as follows: pH=6.9; vitamin solution=1.28% (v/v); glucose=5.01% (w/v) and yeast extract=6.0% (w/v).


Subject(s)
Culture Media/chemistry , Lactobacillus/growth & development , Probiotics , Bacteriological Techniques , Colony Count, Microbial , Food Microbiology , Hydrogen-Ion Concentration , Lactobacillus/metabolism , Models, Biological , Regression Analysis , Vitamins/analysis , Vitamins/metabolism
4.
Folia Microbiol (Praha) ; 46(3): 197-204, 2001.
Article in English | MEDLINE | ID: mdl-11702403

ABSTRACT

A study of the kinetics and performance of solvent-yielding batch fermentation of individual sugars and their mixture derived from enzymic hydrolysis of sago starch by Clostridium acetobutylicum showed that the use of 30 g/L gelatinized sago starch as the sole carbon source produced 11.2 g/L total solvent, i.e. 1.5-2 times more than with pure maltose or glucose used as carbon sources. Enzymic pretreatment of gelatinized sago starch yielding maltose and glucose hydrolyzates prior to the fermentation did not improve solvent production as compared to direct fermentation of gelatinized sago starch. The solvent yield of direct gelatinized sago starch fermentation depended on the activity and stability of amylolytic enzymes produced during the fermentation. The pH optima for alpha-amylase and glucoamylase were found to be at 5.3 and 4.0-4.4, respectively. alpha-Amylase showed a broad pH stability profile, retaining more than 80% of its maximum activity at pH 3.0-8.0 after a 1-d incubation at 37 degrees C. Since C. acetobutylicum alpha-amylase has a high activity and stability at low pH, this strain can potentially be employed in a one-step direct solvent-yielding fermentation of sago starch. However, the C. acetobutylicum glucoamylase was only stable at pH 4-5, maintaining more than 90% of its maximum activity after a 1-d incubation at 37 degrees C.


Subject(s)
1-Butanol/metabolism , Acetone/metabolism , Clostridium/metabolism , Ethanol/metabolism , Starch/metabolism , Amylases/metabolism , Anaerobiosis , Carbohydrate Metabolism , Carbon/metabolism , Clostridium/growth & development , Fermentation , Gelatin , Glucan 1,4-alpha-Glucosidase/metabolism , Hydrolysis , Solvents/metabolism
5.
Environ Technol ; 22(6): 697-704, 2001 Jun.
Article in English | MEDLINE | ID: mdl-11482390

ABSTRACT

Research was undertaken to investigate the treatment of fishery washing water using Bacillus sphaericus, and to recover the spores for subsequent use as bioinsecticide to control the population of mosquitoes. This treatment method could reduce pollution due to organic matter by decreasing the value of Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) by about 85% and 92%, respectively. The maximum concentration of spores (83.3 x 10(7) spores ml(-1)) using normal concentration of filtered fishery washing water was only about 27% lower than that obtained in fermentation using 0.25% (w/v) yeast extract. The larvicidal activity of the spores produced in fermentation using fishery washing water to Culex quinquefaciatus, as measured by LD50 after 48 h, was almost the same as the larvicidal activity of spores obtained from fermentation using yeast extract.


Subject(s)
Bacillus , Conservation of Natural Resources , Fisheries , Waste Disposal, Fluid/methods , Animals , Biodegradation, Environmental , Culicidae , Environmental Pollution/prevention & control , Fermentation , Insect Control , Larva , Lethal Dose 50 , Oxygen/metabolism , Spores , Toxicity Tests
6.
J Agric Food Chem ; 48(9): 4432-8, 2000 Sep.
Article in English | MEDLINE | ID: mdl-10995375

ABSTRACT

The effects of medium strategy, number of impellers, aeration mode, and mode of operation on Morinda elliptica cell suspension cultures in a stirred-tank bioreactor are described. A lower number of impellers and continuous aeration contributed toward high cell growth rate, whereas a higher number of impellers reduced cell growth rate, although not anthraquinone yield. The semicontinuous mode could indirectly imitate the larger scale version of production medium strategy and improved anthraquinone production even with 0. 012% (v/v) antifoam addition. Production medium promoted both growth (maximum dry cell weight of 24.6 g/L) and anthraquinone formation (maximum content of 19.5 mg/g of dry cell weight), without any necessity for antifoam addition. Cultures in production medium or with higher growth rate and anthraquinone production were less acidic than cultures in growth medium or with lower growth rate and anthraquinone production. Using the best operating variables, growth of M. elliptica cells (24.6 g/L) and anthraquinone yield (0.25 g/L) were 45% and 140%, respectively, lower than those using a shake flask culture after 12 days of cultivation.


Subject(s)
Anthraquinones/metabolism , Plants/metabolism , Bioreactors , Cell Culture Techniques , Plant Cells
7.
Folia Microbiol (Praha) ; 43(5): 459-64, 1998.
Article in English | MEDLINE | ID: mdl-9867479

ABSTRACT

Direct conversion of gelatinized sago starch into kojic acid by Aspergillus flavus strain having amylolytic enzymes was carried out at two different scales of submerged batch fermentation in a 250-mL shake flask and in a 50-L stirred-tank fermentor. For comparison, fermentations were also carried out using glucose and glucose hydrolyzate from enzymic hydrolysis of sago starch as carbon sources. During kojic acid fermentation of starch, starch was first hydrolyzed to glucose by the action of alpha-amylase and glucoamylase during active growth phase. The glucose remaining during the production phase (non-growing phase) was then converted to kojic acid. Kojic acid production (23.5 g/L) using 100 g/L sago starch in a shake flask was comparable to fermentation of glucose (31.5 g/L) and glucose hydrolyzate (27.9 g/L) but in the 50-L fermentor was greatly reduced due to non-optimal aeration conditions. Kojic acid production using glucose was higher in the 50-L fermentor than in the shake flask.


Subject(s)
Aspergillus flavus/metabolism , Mycotoxins/biosynthesis , Pyrones/metabolism , Starch/metabolism , Aspergillus flavus/growth & development , Fermentation , Glucan 1,4-alpha-Glucosidase/metabolism , Glucose/metabolism , Hydrolysis , alpha-Amylases/metabolism
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