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1.
Influence of initial cellulose concentration on the carbon flow distribution during batch fermentation by Clostridium thermocellum ATCC 27405 总被引:1,自引:0,他引:1
The objective of this research was to understand how carbon loading influences hydrogen (H2) synthesis and metabolic flow patterns in the thermophilic, cellulolytic bacterium, Clostridium thermocellum. C. thermocellum was cultivated in batch cultures with high (5 g L−1) and low (1 g L−1) initial concentrations of α-cellulose at 60°C. The growth rate of C. thermocellum was 22% lower (0.15 h−1) in cultures with low-cellulose concentration compared with cultures with high-cellulose concentrations. Although substrate
depletion coincided with the end of log-growth in low-cellulose cultures, the prime reason for growth arrest in high-cellulose
cultures was not identified. Ethanol, acetate, and formate were the major soluble end-products with concomitant release of
H2 and CO2 under both conditions. Lactate appeared during the late log phase in high-carbon cultures when pH dropped below 6.4 and became
the major end-product in stationary phase. During the exponential phase of cell growth, significantly higher yields for H2 and acetate (1.90 ± 0.14 and 1.11 ± 0.04 mol/mol glucose equivalent, respectively) were obtained from low-cellulose cultures
compared to those from high-cellulose cultures. The maximum specific rate of H2 production, 6.41 ± 0.13 mmol H2/g dry cell/h, obtained during the exponential phase from low-carbon cultures was about 37% higher than that obtained from
high-carbon cultures. 相似文献
2.
In these studies, butanol (acetone butanol ethanol or ABE) was produced from wheat straw hydrolysate (WSH) in batch cultures
using Clostridium beijerinckii P260. In control fermentation 48.9 g L−1 glucose (initial sugar 62.0 g L−1) was used to produce 20.1 g L−1 ABE with a productivity and yield of 0.28 g L−1 h−1 and 0.41, respectively. In a similar experiment where WSH (60.2 g L−1 total sugars obtained from hydrolysis of 86 g L−1 wheat straw) was used, the culture produced 25.0 g L−1 ABE with a productivity and yield of 0.60 g L−1 h−1 and 0.42, respectively. These results are superior to the control experiment and productivity was improved by 214%. When
WSH was supplemented with 35 g L−1 glucose, a reactor productivity was improved to 0.63 g L−1 h−1 with a yield of 0.42. In this case, ABE concentration in the broth was 28.2 g L−1. When WSH was supplemented with 60 g L−1 glucose, the resultant medium containing 128.3 g L−1 sugars was successfully fermented (due to product removal) to produce 47.6 g L−1 ABE, and the culture utilized all the sugars (glucose, xylose, arabinose, galactose, and mannose). These results demonstrate
that C. beijerinckii P260 has excellent capacity to convert biomass derived sugars to solvents and can produce over 28 g L−1 (in one case 41.7 g L−1 from glucose) ABE from WSH. Medium containing 250 g L−1 glucose resulted in no growth and no ABE production. Mixtures containing WSH + 140 g L−1 glucose (total sugar approximately 200 g L−1) showed poor growth and poor ABE production.
Mention of trade names or commercial products in this article is solely for the purpose of providing scientific information
and does not imply recommendation or endorsement by the United States Department of Agriculture. 相似文献
3.
The effects of temperature (20, 24 and 28 °C) and irradiance (15 and 40 μmol photon m−2 s−1) on the nitrate and ammonium uptake rates of the subtropical red alga, Laurencia brongniartii, were investigated to prepare for tank cultivation. Nitrate uptake followed saturation kinetics and was faster at higher
irradiances and temperatures. In contrast, ammonium uptake was linear over the experimental range and was not affected by
an increase in temperature. A parameter, β, was calculated to compare substrate uptake rates of nitrate along the linear portion
of the uptake curve with that of ammonium. For nitrate, β was lower at low irradiance and higher at high irradiance (β = 0.007
± 0.003 and 0.030 ± 0.002 [μmol N L−1 (μmol N gww−1 d−)−1], respectively). However, β was 0.023 ± 0.002 and 0.034 ± 0.002 [μmol N L−1 (μmol N gww−1 d−1)−1] for ammonium, suggesting a preference for ammonium over nitrate. 相似文献
4.
This work was aimed at producing inulinase by solid-state fermentation of sugarcane bagasse, using factorial design to identify
the effect of corn steep liquor (CSL) and soybean bran concentration, particle size of bagasse and size of inoculum. Maximum
inulinase activity achieved was 250 U per g of dry substrate (gds) at 20% (w/w) of CSL, 5% (w/w) of soybean bran, 1 × 1010 cells mL−1 and particle size of bagasse in the range 9/32 mesh. The use of soybean bran decreased the time to reach maximum activity
from 96 to 24 h and the maximum productivity achieved was 8.87 U gds−1 h−1. The maximum activity was obtained at pH 5.0 and 55.0°C. Within the investigated range, the enzyme extract was more thermostable
at 50.0°C, showing a D-value of 123.1 h and deactivation energy of 343.9 kJ gmol−1. The extract showed highest stability from pH 4.5 to 4.8. Apparent K
m and V
max are 7.1 mM and 17.79 M min−1, respectively. 相似文献
5.
The effect of agitation and aeration on the growth and antibiotic production by Xenorhabdus nematophila YL001 grown in batch cultures were investigated. Efficiency of aeration and agitation was evaluated through the oxygen mass
transfer coefficient (K
L
a). With increase in K
L
a, the biomass and antibiotic activity increased. Activity units of antibiotic and dry cell weight were increased to 232 U ml−1 and 19.58 g l−1, respectively, productivity in cell and antibiotic was up more than 30% when K
L
a increased from 115.9 h−1 to 185.7 h−1. During the exponential growth phase, DO concentration was zero, the oxygen supply was not sufficient. So, based on process
analysis, a three-stage oxygen supply control strategy was used to improved the DO concentration above 30% by controlling
the agitation speed and aeration rate. The dry cell weight and activity units of antibiotic were further increased to 24.22 g l−1 and 249 U ml−1, and were improved by 24.0% and 7.0%, compared with fermentation at a constant agitation speed and a constant aeration rate
(300 rev min−1, 2.5 l min−1). 相似文献
6.
Lakkana Laopaiboon Pornthap Thanonkeo Prasit Jaisil Pattana Laopaiboon 《World journal of microbiology & biotechnology》2007,23(10):1497-1501
Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations.
The optimum initial cell and sugar concentrations in the batch fermentation were 1 × 108 cells ml−1 and 24 °Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y
ps) and productivity (Q
p
) were 100 g l−1, 0.42 g g−1 and 1.67 g l−1 h−1 respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar
concentration of 24 °Bx was one-time substrate feeding, where P, Y
ps and Q
p
were 120 g l−1, 0.48 g g−1 and 1.11 g l−1 h−1 respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of
ethanol concentration and product yield. 相似文献
7.
Comparative ultrastructural analysis of the conducting and non-conducting phloem cells in the common straight-grained silver
birch (Betula pendula var. pendula) and the Karelian birch (B. pendula var. carelica) with abnormal patterned wood was carried out, leading to the conclusion that there is an elevated sucrose content in the
conducting phloem of the Karelian birch. A connection between sucrose levels and formation of abnormalities in the development
of conducting tissues in the Karelian birch trunk was surmised. Experiments in which exogenous sucrose was applied to the
silver birch trunk tissues have demonstrated the effects of different sucrose concentrations (0 g L−1, 10 g L−1, 25 g L−1, 50 g L−1, 100 g L−1) on the formation of xylem and phloem structural elements, and they yielded the types of tissue development that correspond
to the abnormal tissue development in the Karelian birch trunk. 相似文献
8.
Jang K. Kim George P. Kraemer Christopher D. Neefus Ik Kyo Chung Charles Yarish 《Journal of applied phycology》2007,19(5):431-440
Porphyra is one of the world’s most valued maricultured seaweeds and has been cultivated for several hundred years in Asia. The objective
of this study was to produce critical information as a guide for the selection of an appropriate Porphyra species from coastal New England for the development of a land-based aquaculture system. Four Northwest Atlantic Porphyra species: P. leucosticta,
P. amplissima, P. linearis and P. umbilicalis, were cultivated for 1 and 2 weeks at saturated light intensities (100–150 μmol photons m−2s−1) and six combinations of ammonium (25 and 250 μmoles L−1) and temperature (10, 15 and 20°C). Specific growth rate (SGR) increased with decreasing temperature in P. leucosticta, P. linearis and P. umbilicalis and increased with increasing temperature in P. amplissima. The SGR of all species was greater at the higher ammonium concentration. Porphyra linearis had the highest SGR, increasing in biomass by approximately 16% day−1. Phycoerythrin (PE) content was higher at 10°C and 250 μmoles L−1 in all species except P. amplissima. The PE content, measured as fresh weight (FW), of P. linearis (29 mg g−1 FW−1) and P. umbilicalis (26 mg g−1 FW−1) was significantly higher than the other two species. Tissue nitrogen content of all species measured in dry weight was on
average 1.45% higher at 250 μmoles L−1 than at 25 μmoles L−1 ammonium concentration. Porphyra umbilicalis had the highest tissue nitrogen contents (6.76%) at 10°C and 250 μmoles L−1 ammonium. Based on these results, P. linearis and P. umbilicalis should be considered as potential candidates for bioremediation with finfish and shellfish mariculture. 相似文献
9.
Lamia Trabelsi Hatem Ben Ouada Hassen Bacha Mohamed Ghoul 《Journal of applied phycology》2009,21(4):405-412
The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial
design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity:
50, 115, 180 μmol photons m−2 s−1). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light
intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising
growth. The highest growth rate (0.414 ± 0.003 day−1) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m−2 s−1) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower
than 30°C and a light intensity higher than 180 μmol photons m−2 s−1. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m−2 s−1), but for the temperature parameter a maximum effect was detectable at 35°C. 相似文献
10.
Kameshnee Naidoo Manimaran Ayyachamy Kugen Permaul Suren Singh 《Bioprocess and biosystems engineering》2009,32(5):689-695
Xanthomonas campestris pv phaseoli produced an extracellular endoinulinase (9.24 ± 0.03 U mL−1) in an optimized medium comprising of 3% sucrose and 2.5% tryptone. X. campestris pv. phaseoli was further subjected to ethylmethanesulfonate mutagenesis and the resulting mutant, X. campestris pv. phaseoli KM 24 demonstrated inulinase production of 22.09 ± 0.03 U mL−1 after 18 h, which was 2.4-fold higher than that of the wild type. Inulinase production by this mutant was scaled up using
sucrose as a carbon source in a 5-L fermenter yielding maximum volumetric (21,865 U L−1 h−1) and specific (119,025 U g−1 h−1) productivities of inulinase after 18 h with an inulinase/invertase ratio of 2.6. A maximum FOS production of 11.9 g L−1 h−1 and specific productivity of 72 g g−1 h−1 FOS from inulin were observed in a fermenter, when the mutant was grown on medium containing 3% inulin and 2.5% tryptone.
The detection of mono- and oligosaccharides in inulin hydrolysates by TLC analysis indicated the presence of an endoinulinase.
This mutant has potential for large-scale production of inulinase and fructooligosaccharides. 相似文献
11.
Myron A. Peck Lawrence J. Buckley David A. Bengtson 《Environmental Biology of Fishes》2006,75(4):419-429
Synopsis The routine swimming speed (S) of three groups of 4, 9 and 32 cm total length (LT) juvenile cod (Gadus morhua) was quantified in the laboratory at 6 – 10 different temperatures (T) between 3.2 and 16.7°C. At temperatures between 5 and 15°C, mean group S increased exponentially with increasing T (S=a ebT) and the effect of temperature (b = 0.082, Q10 = 2.27) was not significantly different among the groups (over the 8-fold difference in fish sizes of early- and post-settlement
juveniles). Differences in mean S among individuals within each group were quite large (coefficient of variation = 40 – 80%). Swimming data for juveniles and
those collected for groups of 0.4, 0.7 and 0.9 cm standard length (LS) larvae were combined to assess the effect of body size on S. At 8°C, S (mm s−1) increased with LS (mm) according to: S = 0.26LSΦ−5.28LS−1, where Φ = 1.55LS−0.08. Relative S (body lengths s−1) was related to LS by a dome-shaped relationship having a maximum value (0.49 body lengths s−1) at 18.5 – 19 mm LS corresponding to the sizes of fish at the end of larval-juvenile metamorphosis. Previous larval cod IBM’s using a cruise-predator
mode likely overestimated rates of foraging (prey searching and encounters) by a factor of ~2, whereas foraging rates in pause-travel
models are closer to estimates of swimming velocities obtained in this and other laboratory studies. 相似文献
12.
Production of 1,3-Propanediol by Clostridium butyricum VPI 3266 in continuous cultures with high yield and productivity 总被引:2,自引:0,他引:2
González-Pajuelo M Andrade JC Vasconcelos I 《Journal of industrial microbiology & biotechnology》2005,32(9):391-396
The effects of dilution rate and substrate feed concentration on continuous glycerol fermentation by Clostridium butyricum VPI 3266, a natural 1,3-propanediol producer, were evaluated in this work. A high and constant 1,3-propanediol yield (around
0.65 mol/mol), close to the theoretical value, was obtained irrespective of substrate feed concentration or dilution rate.
Improvement of 1,3-propanediol volumetric productivity was achieved by increasing the dilution rate, at a fixed feed substrate
concentration of 30, 60 or 70 g l−1. Higher 1,3-propanediol final concentrations and volumetric productivities were also obtained when glycerol feed concentration
was increased from 30 to 60 g l−1, at D=0.05–0.3 h−1, and from 60–70 g l−1, at D=0.05 and 0.1 h−1·30 g l−1 of 1,3-propanediol and the highest reported value of productivity, 10.3 g l−1 h−1, was achieved at D=0.30 h−1 and 60 g l−1 of feed glycerol. A switch to an acetate/butyrate ratio higher than one was observed for 60 g l−1 of feed glycerol and a dilution rate higher than 0.10 h−1; moreover, at D=0.30 h−1 3-hydroxypropionaldehyde accumulation was observed for the first time in the fermentation broth of C. butyricum. 相似文献
13.
Nitrogenous excretion in two snails, Littorina saxatilis (high intertidal) and L. obtusata (low intertidal) was studied in relation to temperature acclimation (at 4° and 21°C), including total N excretion rates,
the fraction of urea in N excretion, corresponding O:N ratios and the partitioning of deaminated protein between catabolic
and anabolic processes at 4°, 11° and 21°C. Aggregate N excretion rates in both species showed no significant compensatory
adjustments following acclimation. Total weight specific N excretion rates at 21°C were higher in standard 3 mg L. saxatilis (739 ng N mg−1 h−1) than standard 5 mg L. obtusata (257 ng N mg−1 h−1) for snails acclimated to 21°C. Comparisons of Q10 values of total weight specific N excretion to Q10 values for weight specific oxygen consumption ({xxV}O2) between 4° to 11 °C and 11° to 21°C indicated that, while total rates of catabolic metabolism ({xxV}O2) and protein deamination in L. obtusata were essentially parallel, the relationship between N excretion and {xxV}O2 in L. saxatilis revealed the partitioning of a larger share of deaminated protein carbon into anabolism at 4° and 21°C than at 11°C. Urea
N accounted for a larger share of aggregate N excreted in L. saxatilis than in L. obtusata, but in both species urea N is a greater proportion of total N excreted when acclimated at 4°C (urea N: ammonia N ratio range:
1 to 2.15) than in snails acclimated to 21°C (urea N: ammonia N ratio range: 0.46 to 1.39). Molar O:N ratios indicate that
the proportion of metabolism supported by protein catabolism is greater in L. saxatilis (O:N range: 2.5–8.4) than in L. obtusata (O:N range: 7.3–13.0). In both species, regardless of acclimation temperature, the O:N ratios are generally lowest (high
protein catabolism) at 4°C and highest at 21°C. 相似文献
14.
Effects of the burrowing mayfly,Hexagenia, on nitrogen and sulfur fractions in lake sediment microcosms 总被引:1,自引:1,他引:0
Effects of the burrowing mayfly, Hexagenia, on nitrogen and sulfur fractions of sediment, and overlying water were determined. Laboratory microcosms were used to reproduce
the benthic environment. The activities of Hexagenia increased sediment Eh (1.98 ± 0.486 (22) mV · day −1), and decreased pH in sediment (−0.007 ± 0.001 (22) day −1) and overlying water(-0.024 ± 0.004 (10) day−1). In the control, Eh decreased and pH did not change. The presence of Hexagenia also markedly increased ammonia in sediment (5.46 ± 0.14 (22) ppm N · day−1) and overlying water (0.792 ± 0.154 (10) ppm N · day−1), while the control did not change. In addition, the sulfate fraction of sediment (0.177 ± 0.006 (17)% dry mass) and water
(50.0 ± 4.9 (5) mg · I−1) in microcosms with Hexagenia was greater than that of the control (0.151 ± 0.005 (16)% dry mass; 14.7 ± 1.71 (3) mg · 1−1) at the termination of the experiment. Hexagenia may also stimulate the mineralization of carbon-bonded sulfur. The general role of Hexagenia in altering sediment chemistry is discussed. 相似文献
15.
We evaluated the combined effects of algal (Chlorella vulgaris) food levels (low, 0.5 × 106 (or 2.9 μg C ml−1); and high, 1 × 106 cells ml−1 (or 5.8 μg C ml−1)) and zinc concentrations (0, 0.125, and 0.250 mg l−1 of ZnCl2) on the competition between two common planktonic rotifers Anuraeopsis fissa and Brachionus rubens using their population growth. Median lethal concentration data (LC50) (mean ± 95% confidence intervals) showed that B. rubens was more resistant to zinc (0.554 ± 0.08 mg l−1) than A. fissa (0.315 ± 0.07 mg l−1). A. fissa when grown alone or with Zn was always numerically more abundant than B. rubens. When grown in the absence of zinc, under low- and high-food levels, the peak abundances of A. fissa varied from 251 ± 24 to 661 ± 77 ind. ml−1, respectively, and the corresponding maxima for B. rubens were 52 ± 3 and 102 ± 18 ind. ml−1. At a given food level, competition for food reduced the peak abundances of both rotifers considerably. Increase in Zn concentration
also lowered the rotifer abundances. The impact of zinc on competition between the two-rotifer species was evident at low-food
level, mainly for A. fissa. At zinc concentrations of 0 and 0.125 mg l−1, the populations of both rotifers continued to grow for about 10 days, but thereafter B. rubens began to decline. Role of zinc on the competitive outcome of the two species is discussed in relation to the changing algal
densities in natural water bodies. 相似文献
16.
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as
a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L−1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L−1 h−1. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L−1 in 26.5 h at a mean growth rate 3.37 g DW L−1 h−1. Mean specific growth rate μ was about 0.1 h−1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from
0.8 to 81.6 g DW L−1 in 66.5 h at a mean growth rate 1.22 g DW L−1 h−1 and μ = 0.07 h−1. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities
higher than 10 g DW L−1) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L−1) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)−1. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping
aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency. 相似文献
17.
C. L. Carretero M. Cantos J. L. García A. Troncoso 《In vitro cellular & developmental biology. Plant》2007,43(4):364-369
Three cassava clones (SOM-1, “05”, and “50”) were cultured in vitro on MS medium plus sucrose (30 g L−1) and myo-inositol (100 mg L−1) without plant growth regulators and with additions of 0 (control), 0.5, 1, 1.5, 2, 2.5, and 3 g L−1 NaCl to test their salt tolerance. The same cassava clones were cultivated in greenhouse conditions on a sandy soil substratum
and irrigated with 20% strength Hoagland solution, and additions of 0, 4, and 8 g L−1 of NaCl. Salinity negatively affected the survival, development, leaf water content, and mineral composition (mainly by accumulation
of Cl and Na) of both in vitro and ex vitro plants, but with different intensity in each clone. In both conditions of culture (in vitro and ex vitro) clone SOM-1, from a desert arid saline zone of Somalia, was the most tolerant and clone “05”, from a rainy region of Ivory
Coast, the most sensitive. Clone “50” tolerance to in vitro salt treatments, although lower, was not significantly different from that of SOM-1 but the ex vitro response was similar to “05”. In general, there was a correlation between in vitro and ex vitro behavior of the cassava plant regarding salt tolerance, which would allow the in vitro culture method to be used for selection of salt-tolerant plants of this crop. 相似文献
18.
Lactobacillus intermedius NRRL B-3693 produced mannitol, lactic acid, and acetic acid when grown on fructose at 37°C. The optimal pH for mannitol production
from fructose by the heterofermentative lactic acid bacterium (LAB) in pH-controlled fermentation was at pH 5.0. It produced
160.7 ± 1.1 g mannitol in 40 h with a volumetric productivity of 4.0 g l−1 h−1 in a simplified medium containing 250 g fructose, 50 g corn steep liquor (CSL), and 33 mg MnSO4 per liter. However, the mannitol production by the LAB was severely affected by the variability of CSL. The supplementation
of CSL with soy peptone (5 g/l), tryptophan (50 mg/l), tryptophan (50 mg/l) plus tyrosine (50 mg/l), or commercial protease
preparation (2 ml/100 g of CSL) enhanced the performance of the inferior CSL and thus helped to overcome the nutrient limitations. 相似文献
19.
Meenakshi Banerjee R. Craig Everroad Richard W. Castenholz 《Extremophiles : life under extreme conditions》2009,13(4):707-716
Cyanobacteria that grow above seawater salinity at temperatures above 45°C have rarely been studied. Cyanobacteria of this
type of thermo-halophilic extremophile were isolated from siliceous crusts at 40–45°C in a geothermal seawater lagoon in southwest
Iceland. Iceland Clone 2e, a Leptolyngbya morphotype, was selected for further study. This culture grew only at 45–50°C, in medium ranging from 28 to 94 g L−1 TDS, It showed 3 doublings 24 h−1 under continuous illumination. This rate at 54°C was somewhat reduced, and death occurred at 58°C. A comparison of the 16S
rDNA sequence with all others in the NCBI database revealed 2 related Leptolyngbya isolates from a Greenland hot spring (13–16 g L−1 TDS). Three other similar sequences were from Leptolyngbya isolates from dry, endolithic habitats in Yellowstone National Park. All 6 formed a phylogenetic clade, suggesting common
ancestry. These strains shared many similarities to Iceland Clone 2e with respect to temperature and salinity ranges and optima. Two endolithic Leptolyngbya isolates, grown previously at 23°C in freshwater medium, grew well at 50°C but only in saline medium. This study shows that
limited genotypic similarity may reveal some salient phenotypic similarities, even when the related cyanobacteria are from
vastly different and remote habitats. 相似文献
20.
H. Li W. Q. Liang Z. Y. Wang N. Luo X. Y. Wu J. M. Hu J. Q. Lu X. Y. Zhang P. C. Wu Y. H. Liu 《World journal of microbiology & biotechnology》2006,22(1):1-7
Summary Response surface methodology was applied to optimize medium components for maximum production of a thermostable α-galactosidase by thermotolerant Absidia sp. WL511. First, the Plackett-Burman screening design was used to evaluate the effects of variables on enzyme production. Among
these variables, MgSO4 and soybean meal were identified as having the significant effects (with confidence level (90%). Subsequently, the concentrations
of MgSO4 and soybean meal were further optimized using central composite designs. The optimal parameters were determined by response
surface and numerical analyses as 0.0503% (g/g) MgSO4 and 0.406% (g/g) soybean meal and allowed α-galactosidase production to be increased from 4.4 IU g−1 to 117.8 IU g−1. The subsequent verification experiments confirmed the validity of the model. The optimum pH of enzymatic activity was 7.5
and the enzyme was stable at pH values ranging from 5.0 to 9.0. The optimum temperature was 73 °С. The enzyme was fairly stable
at temperatures up to 60 °С and had 87% of its full activity at 65 °С after 2 h of incubation. 相似文献