Investigations on neomycin production with immobilized cells of<Emphasis Type="Italic">Streptomyces marinensis</Emphasis> Nuv-5 in calcium alginate matrix

The purpose of this investigation was to study the effect ofStreptomyces marinensis NUV-5 cells immobilized in calcium alginate for the production of neomycin. The effect of various parameters, such as the effect of alginate concentration (1%, 2%, 3%, 4%, and 5% wt/vol), the effect of cation (caCl₂, BaCl₂, and SrCl₂), the concentration of cation (0.01M, 0.125M, 0.25M, 0.375M, and 0.5M), the curing times (1, 6, 11, 16, and 21 hours), and the diameter of the bead (1.48, 2.16, 3.24, 4.46, and 5.44 mm), on neomycin production and bead stability were studied. The effect of maltose (4%, 3%, 2%, and 1% wt/vol) and sodium glutamate (0.6%, 0.3%, 0.15%, and 0.075%) wt/vol) concentration on neomycin production was also studied. Better neomycin production was achieved with optimized parameters, such as alginate at 2% wt/vol, 0.25M CaCl₂, 1-hour curing time, and 3.24 mm bead diameter. Effective neomycin production was achieved with 3% wt/vol maltose and 0.6% wt/vol sodium glutamate concentration. The repeated batch fermentations were conducted (every 96 hours) using the optimized alginate beads, employing the production medium with 3% wt/vol maltose and 0.6% wt/vol sodium glutamate along with minerals salts solution. The increase in antibiotic production was observed up to the 5th cycle, and later gradual decrease in antibiotic production was observed. Comparison of the total antibiotic production with free cells and immobilized cells was also done. An enhanced antibiotic productivity of 32% was achieved with immobilized cells over the conventional free-cell fermentation, while 108% more productivity was achieved over the washed free-cell fermentation. From these results it is concluded that the immobilized cells ofS marinensis NUV-5 in calcium alginate are more efficient for the production of neomycin with repeated batch fermentation.     

Optimization of α‐Amylase Immobilization in Calcium Alginate Beads

Abstract

α‐Amylase enzyme was produced by Aspergillus sclerotiorum under SSF conditions, and immobilized in calcium alginate beads. Effects of immobilization conditions, such as alginate concentration, CaCl₂ concentration, amount of loading enzyme, bead size, and amount of beads, on enzymatic activity were investigated. Optimum alginate and CaCl₂ concentration were found to be 3% (w/v). Using a loading enzyme concentration of 140 U mL^?1, and bead (diameter 3 mm) amount of 0.5 g, maximum enzyme activity was observed. Beads prepared at optimum immobilization conditions were suitable for up to 7 repeated uses, losing only 35% of their initial activity. Among the various starches tested, the highest enzyme activity (96.2%) was determined in soluble potato starch hydrolysis for 120 min at 40°C.     

Overexpression of alginate lyase of <Emphasis Type="Italic">Pseudoalteromonas elyakovii</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis>, purification,and characterization of the recombinant alginate lyase

The alyPEEC gene encoding alginate lyase from marine bacterium Pseudoalteromonas elyakovii IAM 14594 was subcloned into pBAD24 with arabinose promoter and sequenced, and overexpressed in TOP10 strain of E. coli after arabinose induction. Expression levels of alyPEEC gene in E. coli cells were over 39.6-fold higher than those in P. elyakovii IAM 14594 cells. The molecular mass of purified alginate lyase from the engineered E. coli cells was estimated to be 32.0 kDa. Optimum pH and temperature of the alginate lyase activity were 7.0 and 30 °C, respectively. The enzyme was unstable on heating and in acidic and alkaline solution. The enzyme activity was stimulated by the MgCl₂, NaCl, KCl, CaCl₂, BaCl₂ and MnCl₂, but was inhibited by the addition of 1.0 mM of EGTA, EDTA, SDS, ZnSO₄, AgNO₃, and CoCl₂. All the alginate, polyM and polyG could be converted into oligosaccharides with more than tetrasaccharides by the purified recombinant alginate lyase, suggesting that the recombinant alginate lyase produced by the engineered E. coli has highly potential application in seaweed genetics, food and pharmaceutical industries.     

Spectrophotometric assay for online measurement of the activity of lipase immobilised on micro-magnetic particles

A spectrophotometric assay has been adapted to directly measure the activity of enzymes immobilised on insoluble magnetic particles. Three different types of lipases (Candida antarctica lipase A and B and Thermocatenulatus lanuginosus lipase) were immobilised on two types of magnetic beads. The activity of the resulting immobilised lipase preparations was measured directly in the reaction solution by using a modified p-nitrophenol ester assay using a spectrophotometer. Removal of the solid particles was not necessary prior to spectrophotometric measurement, thus allowing reliable kinetic measurements to be made rapidly. The method was effective for a wide range of magnetic bead concentrations (0.01–0.2 mg ml⁻¹). In all cases the assay could determine the bead-related specific enzyme activity. The assay was validated by comparing with a pH-stat method using p-nitrophenol palmitate as the substrate with an excellent correlation between the two methods. The utility of the spectrophotometric assay was demonstrated by applying it to identify the best combination of lipase type, activation chemistry and magnetic particle. Epoxy activation of poly vinyl alcohol-coated magnetic particles prior to immobilisation of commercial C. antarctica lipase A gave the best preparation.     

Influence of immobilization parameters on growth and lactic acid production by <Emphasis Type="Italic">Streptococcus thermophilus</Emphasis> and <Emphasis Type="Italic">Lactobacillus bulgaricus</Emphasis> co-immobilized in calcium alginate gel beads

Streptococcus thermophilusand Lactobacillus bulgaricus were co-immobilized in different systems with varying calcium (0.1–1.5M) and alginate (1–2<><>, w/v) concentrations. Highest lactic acid production was 35 g l₁ when both bacteria were in high viscosity beads (1<><>, w/v alginate) hardened in 0.1 M CaCl₂ .The gel bead composition affected size and distribution of entrapped lactic acid bacteria.     

Encapsulation of astaxanthin-rich Xanthophyllomyces dendrorhous for antioxidant delivery

Calcium alginate gel (CAG) beads were used to entrap the antioxidant astaxanthin-rich Xanthophyllomyces dendrorhous (ASX) by ionic gelation. ASX-CAG bead entrapment efficiency and release behavior, as influenced by alginate and CaCl₂ concentration and hardening time, were investigated. The optimized bead preparation conditions that gave rise to an efficient ASX release pattern were 1.5% alginate, 50 mM CaCl₂, and a 5 min hardening time. The antioxidant activity of non-encapsulated ASX was maintained for 4 days and then sharply decreased, whereas encapsulated ASX was maintained for 6 days. These results revealed that physical entrapment of ASX within CAG beads could be an effective technique for protecting the antioxidant activity of ASX from lipid peroxidation.     

Determination of the radial distribution of Saccharomyces cerevisiae immobilised in calcium alginate gel beads

Summary The dissolution of alginate gel beads in 20 g sodium citrate /l produces a linear decrease in bead diameter. The rate of dissolution is dependent on the concentration of CaCl₂ within the gel beads. This method allows the controlled release of Saccharomyces cerevisiae from alginate gel beads and permits the simple and rapid determination of the radial distribution of cell concentration.     

Detoxification of hexavalent chromate by Amphibacillus sp. KSUCr3 cells immobilised in silica-coated magnetic alginate beads

Recently isolated Cr(VI)-reducing Amphibacillus KSUCr3 whole cells were immobilised in magnetic gels. Magnetic magnetite (Fe₃O₄) nanoparticles were synthesised with an average particle size of 47 nm and 80 electromagnetic unit (emu)/g saturation magnetisation. Whole cells were immobilised by entrapment in agar, agarose, alginate, or gelatin in the presence or absence of Fe₃O₄ nanoparticles for the preparation of both magnetic and nonmagnetic immobilised cells. Of the gels tested, alginate was selected as the best immobilisation matrix, and following optimisation of the entrapment process, the immobilisation yield reached 92.5%. In addition to the ease of separation and reuse of the magnetic cell-containing alginate beads using an external magnet, the magnetically immobilised cells showed approximately 16% higher Cr(VI) reduction activity compared with nonmagnetic immobilised cells. To improve their physical and mechanical properties, the magnetic alginate beads were successfully coated with a dense silica layer using sol-gel chemistry and Ca(OH)₂, an alkaline catalyst for tetraethyl orthosilicate, to avoid leaching of Ca²⁺ ions. Amphibacillus KSUCr3 cells immobilised in silica-coated magnetic alginate beads showed approximately 1.4- to 3.9-fold enhancement of thermal stability compared with free cells. Furthermore, after seven batch cycles, the Cr(VI) reduction activity of free cells decreased to 48%, whereas immobilised cells still retained 81.1% of their original activity. In addition, the Cr(VI)-reduction rate of immobilised cells was higher relative to free cells, especially at higher Cr(VI) concentrations. These results supported the development of a novel, efficient biocatalysts for Cr(VI) detoxification using a combination of whole cell immobilisation, sol-gel chemistry, and nanotechnology.     

Effect of exogenous calcium on post-thaw growth recovery and subsequent plant regeneration of cryopreserved embryogenic calli of <Emphasis Type="Italic">Hevea brasiliensis</Emphasis> (Müll. Arg.)

A reliable cryopreservation technique was developed for friable embryogenic callus lines of Hevea brasiliensis. The study showed that reducing the CaCl₂ concentration of the pre-culture medium from 9 mM to 1 or 0 mM CaCl₂ before cryopreservation promoted post-thaw callus growth, 1 mM being the optimum CaCl₂ concentration for embryo regeneration. Post-thaw callus proliferation decreased in line with the increase of plated callus weight. The effect of cryopreservation was assessed on 39 independent lines showing that cryopreservation did not affect embryogenic and plant regeneration for a majority of lines. The decrease in CaCl₂ concentration of the pre-culture medium led to a drop in callus calcium content indicating a direct link between the CaCl₂ concentration of the pre-culture medium and the endogenous calcium content of the calli. It also highlighted the implication of tissue calcium content in cryotolerance. Callus water status and the different ways by which calcium could prevent cryoinjury is also discussed.     

Dye decolorisation by laccase entrapped in copper alginate

A novel immobilisation system was developed for dye decolorisation using laccase produced by Ganoderma sp. KU-Alk4. The enzyme showed high efficiency in dye decolorisation when entrapped in Cu–Al and Cu-alginate beads. The former gave the highest activity but the enzyme activity survived longer in the latter. An experimental design of two 3 × 3 Latin Square experiments was applied to evaluate the effects of three different alginate compositions (low, intermediate and high mannuronate), concentration of alginate, (1.5, 3.0 and 4.5% w/v) and concentration of cross-linking agent, CuSO₄ (0.075, 0.15 and 0.225 M) on the decolorisation of indigo carmine dye and residual laccase activity in beads. The most significant factor for residual activity was the concentration of the cross-linking agent (P < 0.05) followed by alginate composition (P < 0.1). Increasing the alginate concentration resulted in only small increase in the dye decolorisation. However, higher laccase activity remained in 3.0% w/v alginate beads. Maximal dye decolorisation was achieved when 3.6% w/v low mannuronate alginate and 0.15 M CuSO₄ was used. Optimal conditions were confirmed in an extended experimental run. Results are presented from 9 successive batch runs over 12 days, reaching 96% removal of the dye (216 mg/l).     

Studies on the accumulation of heavy metal elements in biological systems

Summary Cells of a Daucus carota suspension culture were entrapped in a matrix of calcium alginate. The immobilised cells, incubated in a buffer mixture of sucrose, nitrate, KCl, CaCl₂, 2-(N-morpholino)-ethane sulphonic acid at pH 5.5, hydroxylated digitoxigenin. When compared under the same incubation conditions, freely suspended cells biotransformed digitoxigenin at a faster rate. Periplogenin formation was maximal at pH 5.3 and temperatures of 26°–34°C. The hydroxylase activity of the entrapped cells adapted to the presence of 20 mM CaCl₂ over a 12 day incubation. The diffusion barrier established on entrapment of the cells could not be overcome by addition of detergents or methanol. Controlled addition of chloroform (at 1/4 and 1/2 saturation) did stimulate hydroxylation of digitoxigenin without adversely affecting cell viability. The rate of hydroxylation of digitoxigenin was linear over an immobilised cell concentration of 0–7 mg dry weight and a digitoxigenin concentration of 0–20 mg/L. Five consecutive batch bioconversions at a rate greater than 60% could be achieved before the biocatalyst was inactivated. The results are discussed in relation to improving the hydroxylation reaction by immobilised D. carota and other reactions performed by immobilised plant cells.     

Degradation of ethylbenzene by free and immobilized <Emphasis Type="Italic">Pseudomonas</Emphasis><Emphasis Type="Italic">fluorescens-</Emphasis>CS2

Pseudomonas fluorescens-CS2 metabolized ethylbenzene as the sole source of carbon and energy. The involvement of catechol as the hydroxylated intermediate during the biodegradation of ethylbenzene was established by TLC, HPLC and enzyme analysis. The specific activity of Catechol 2,3-dioxygenase in the cell free extracts of P. fluorescens-CS2 was determined to be 0.428 μmoles min⁻¹ mg⁻¹ protein. An aqueous-organic, Two-Phase Batch Culture System (TPBCS) was developed to overcome inhibition due to higher substrate concentrations. In TPBCS, P. fluorescens-CS2 demonstrated ethylbenzene utilization up to 50 mM without substrate inhibition on inclusion of n-decanol as the second phase. The rate of ethylbenzene metabolism in TPBCS was found enhance by fivefold in comparison with single phase system. Alternatively the alginate, agar and polyacrylamide matrix immobilized P. fluorescens-CS2 cells efficiently degraded ethylebenzene with enhanced efficiency compared to free cell cultures in single and two-phase systems. The cells entrapped in ployacrylamide and alginate were found to be stable and degradation efficient for a period of 42 days where as agar-entrapped P. fluorescens was stable and efficient a period of 36 days. This demonstrates that alginate and polyacrylamide matrices are more promising as compared to agar for cell immobilization.     

外源CaCl2对NaCl胁迫下酸枣幼苗氮代谢的影响

为了研究CaCl₂对NaCl胁迫下酸枣幼苗根、茎、叶的氮代谢影响,探索钙缓解幼苗NaCl胁迫的作用途径。该研究以酸枣幼苗为试验材料,检测不同浓度CaCl₂(0、5、10、20 mmol/L)对NaCl(150 mmol/L)胁迫下幼苗叶片H₂O₂、O^-·₂含量,根、茎、叶中硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)活性及游离氨基酸、可溶性蛋白、硝态氮含量的影响,并采用主成分分析法筛选出评价CaCl₂缓解NaCl胁迫效应的生理指标。结果表明：与NaCl胁迫相比,盐胁迫幼苗叶片的H2O₂、O^-·₂积累量在5、10 mmol/L CaCl₂处理下显著减少;GOGAT活性在5、10 mmol/L CaCl₂处理下的植株根和茎内以及各浓度 CaCl₂处理的叶内均显著升高, GS、NR活性在10、20 mmol/L CaCl₂处理的根内和10 mmol/L CaCl₂处理的茎内以及5、10、20 mmol/L CaCl₂处理的叶内均显著升高;可溶性蛋白含量在5、10、20 mmol/L CaCl₂处理的根、茎、叶内均显著升高,游离氨基酸含量在10、20 mmol/L CaCl₂处理的根和茎内以及10 mmol/L CaCl₂处理的叶内均显著升高,硝态氮含量在10 mmol/L CaCl₂处理的根和茎内以及5、10、20 mmol/L CaCl₂处理的叶内均显著升高。研究发现,150 mmol/L NaCl胁迫对酸枣幼苗造成明显过氧化伤害,抑制了体内氮代谢;外源CaCl₂可通过促进幼苗根和茎内GS/GOGAT循环对NH₄⁺的同化作用,提高叶片NR活性,加快硝态氮的转化速率,从而增强幼苗对NaCl胁迫的适应性,并以10 mmol/L CaCl₂处理缓解效果最佳;游离氨基酸、GOGAT、NR可以作为CaCl₂缓解幼苗NaCl胁迫伤害的评价指标。     

Resolution of N-(2-ethyl-6-methylphenyl) alanine by using microgel beads containing Pseudomonas cepacia lipase

Abstract

Pseudomonas cepacia lipase (PCL) was immobilized in alginate microgel beads by electrostatic dispersion. The high electrical potential applied in the immobilization process could significantly decrease the droplet size. The optimum conditions for lipase immobilization were 2% (w/v) alginate, 100 mM CaCl₂, 8 mg/mL enzyme, 4 kV electrical potential and 200 μm mean bead size. Under these conditions, 78.2 U/g of immobilized PCL activity was obtained with 39.1% retained activity and 57.2% immobilization efficiency. The immobilized PCL (PCL-CA) was subsequently used in the enantioselective hydrolysis of (R, S)-N-(2-ethyl-6-methylphenyl) alanine methyl ester. Although PCL-CA exhibited slightly lower activity than free PCL, it preserved the high enantioselectivity (E-value >?200), which afforded enantiomerically pure (R)-acid (99% e.e._p). Furthermore, PCL-CA exhibited higher thermal stability, storage and medium stability than that of free PCL. Batch-wise operational stability studies demonstrated that PCL-CA retained its initial activity for at least 10 cycles of hydrolysis.     

Parametric Studies on Batch Degradation of a Plasticizer Di-n-Butylphthalate by Immobilized Bacillus sp

Summary Di-n-butylphthalate (DBP) is one of the phthalate esters (PAEs) used in the manufacture of plasticizers, insect repellents and synthetic fibres and contributes to environmental pollution. We report a novel bacterium belonging to the genus, Bacillus (NCIM 5220), which has the ability to utilize DBP as the sole source of carbon and energy. This bacterium was immobilized in alginate. The degradation of DBP by immobilized cells was compared with free cells. The effects on the degradation of DBP of different factors like gel (alginate) concentration, gel bead size, temperature, and pH were investigated. Oxygen uptake in the presence of DBP by free and immobilized cells was also studied. The results showed that the degradation of DBP by immobilized cells was more efficient than by free cells. Further, the effect of various factors tested on the degradation of DBP by alginate-immobilized cells showed that the degradation of DBP was remarkably affected by alginate concentration between 2 and 5% and drastically decreased between bead size 2 and 5 mm. A change of 10 °C of reaction temperature from 30 to 40 °C did not alter the degradation of DBP, and maximum degradation was appeared to be favoured over a broad pH range of 6.5–7.5 for immobilized cells as compared to free cells, which showed an optimum temperature of about 35 °C and pH of 7.0. The immobilized cells showed higher oxidation of DBP than free cells. Thus more efficient degradation of DBP could be achieved by immobilizing Bacillus sp. in alginate beads.     

Localization of glycollate dehydrogenase in Dunaliella salina

Glycollate dehydrogenase of the halotolerant green alga Dunaliella salina, isolated from a brine pond, was found associated with the membrane fraction which exhibited complete photosynthetic activity. Highest enzyme activity was found in cells grown in the presence of 5% NaCl. Any increase in NaCl concentration led to a decrease in specific enzyme activity.Abbreviations PSI(II) photosystem I(II)     

Increasing NaCl and CaCl<Subscript>2</Subscript> concentrations in the growth medium of quince leaves: I. Effects on somatic embryo and root regeneration

Summary The effects of increasing concentrations of NaCl and CaCl₂ on quince (Cydonia oblonga Mill. BA 29 clone) somatic embryogenesis and adventitious root regeneration were investigated. Leaves collected from in vitro-grown shoots were used as explants and induced for 2d in liquid Murashige and Skoog medium containing 11.3 μM 2,4-dichlorophenoxyacetic acid. Explants were then cultured on semisolid Murashige and Skoog medium enriched with 4.7 μM kinetin and 0.5 μM naphthaleneacetic acid under red light for 25 d and under white light for another 25 d. Two experiments were performed: in the first, NaCl was used at 0,25, 50, 100, and 200 mM in factorial combination with CaCl₂ at 3, 9, and 27 mM; in the second, NaCl was applied at 0, 5, 10, 20, 40, and 80 mM in combination with CaCl₂ at 0.3, 1.0, and 3.0 mM. Quince leaves revealed the capacity to regenerate somatic embryos and/or adventitious roots. Quantitative and qualitative regeneration from leaves was affected by NaCl treatments: increasing NaCl concentrations, in combination with CaCl₂ at 1 mM, led to an increase in the proportion of leaves producing somatic embryos only, and to a decrease of both leaves regenerating roots only and leaves simultaneously producing somatic embryos and adventitious roots. This suggests a beneficial effect of salt stress on the embryogenic process. The regeneration response decreased with increasing salt concentrations and was almost totally inhibited above 50 mM NaCl and 9 mM CaCl₂. The presence of CaCl₂ in the culture medium apparently mitigated the effects of salt stress, but only when NaCl was applied at 40 mM. NaCl at 5 mM, in the presence of 0.3 or 1 mM CaCl₂, was favorable both to somatic embryo and root production. No value of the ratio Na⁺/Ca²⁺ was found to be optimal for the regeneration processes.     

Screening of Catalytically Active Microorganisms for the Synthesis of 6-Modified Purine Nucleosides

Modified nucleosides can be prepared by microbial transglycosylation from cheaper nucleoside precursors using free or immobilised whole cells. An efficient screening method to find transglycosylation activity in␣microorganisms was developed for the synthesis of 6-modified purine nucleosides, such as 6-chloro-, 6-methoxy-, 6-iodo- and 6-mercaptopurine ribonucleoside. Out of 100 microorganisms screened, Bacillus stearothermophilus ATCC 12980 was the best for this purpose.     

Immobilization of Xylan-Degrading Enzymes from Scytalidium thermophilum on Eudragit L-100

Summary Xylanase from Scytalidium thermophilum was immobilized on Eudragit L-100, a pH sensitive copolymer of methacrylic acid and methyl methacrylate. The enzyme was non-covalently immobilized and the system expressed 70% xylanase activity. The immobilized preparation had broader optimum temperature of activity between 55 and 65 °C as compared to 65 °C in case of free enzyme and broader optimum pH between 6.0 and 7.0 as compared to 6.5 in case of free enzyme. Immobilization increased the t_1/2 of enzyme at 60 °C from 15 to 30 min with a stabilization factor of 2. The K_m and V_max values for the immobilized and free xylanase were 0.5% xylan and 0.89 μmol/ml/min and 0.35% xylan and 1.01 μmol/ml/min respectively. An Arrhenius plot showed an increased value of activation energy for immobilized xylanase (227 kcal/mol) as compared to free xylanase (210 kcal/mol) confirming the higher temperature stability of the free enzyme. Enzymatic saccharification of xylan was also improved by xylanase immobilization.     

Enhanced hydantoinase and N-carbamoylase activity on immobilisation of Agrobacterium tumefaciens

Cell extracts of Agrobacterium tumefaciens, immobilised in calcium alginate beads, had a 7-fold increase in N-carbamoylase (N-carbamylamino acid amidohydrolase E.C. 3.5.1) activity on reaction with N-carbamylglycine. The hydantoinase (dihydropyrimidinase E.C. 3.5.2.2) and N-carbamoylase activities remained stable over 4 weeks storage at 4°C relative to the non-immobilised enzymes, with the hydantoinase activity showing a 5-fold increase in activity relative to the non-immobilised hydantoinase. The pH optima of the immobilised hydantoinase and N-carbamoylase enzymes decreased to pH 7 and pH 8, respectively. The temperature optimum remained at 40°C for the N-carbamoylase enzyme while the hydantoinase activity was optimal at 50°C.