Suitable Carbon Source Research Articles

Effect of quinoid redox mediators during azo dye decolorization by anaerobic sludge: Considering the catalyzing mechanism and the methane production

The effects of quinoid compounds on azo dyes decolorization were studied. Compared with other quinones, menadione was the most effective at aiding azo dye decolorization. Sodium formate was a suitable carbon source for the anaerobic decolorization system. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis indicated that the microbial structure changed in response to varying carbon sources. Phylogenetic analysis showed that the anaerobic sludge was consisted mainly of nine genera. The mechanism studies showed that the biotransformation of menadione to its hydroquinone form was the rate-limiting step in the dye decolorization process. Moreover, study of the electron transfer mechanism of quinone-mediated reduction showed that azo dye decolorization is not a specific reaction. The NADH chain was involved in the decolorization process. The methane production test indicated that azo dyes had an inhibitory effect on methane production. However, supplementation with a redox mediator could recover the inhibited methanogenesis. High-throughput sequencing analysis revealed that the methanogenic archaeal community was altered in the anaerobic sludge with or without azo dyes and the redox mediator.

High-performance SiO/C as anode materials for lithium-ion batteries using commercial SiO and glucose as raw materials

Silicon monoxide (SiO) is considered as a promising anode material for lithium-ion batteries (LIBs) due to its higher capacity and longer cycle life than those of graphite and silicon, respectively. In this study, glucose was developed as a suitable and inexpensive carbon source to synthesize SiO/C composite with a high performance. In addition, the effects of the calcination temperature and the amount of carbon source on the electrochemical performance of the SiO/C composite were investigated. The addition of 5 wt% glucose and a calcination temperature of 800 °C demonstrated the optimum conditions for SiO/C synthesis. The resultant SiO/C showed an initial charge capacity of 1259 mAh·g−1 and a high initial coulombic efficiency of 71.9%. A charge capacity of 850 mAh·g−1 after 100 cycles at 200 mA·g−1 was achieved, demonstrating the best value of the SiO/C-based materials. The composition changes of SiO under the calcination temperature played a significant role in the electrochemical performance. Overall, the obtained SiO/C material with a high capacity and good stability is suitable for LIB applications as an anode material.

Optimized production and safety evaluation of hispidin-enriched Sanghuangporus sanghuang mycelia.

Phellinus linteus, also known as the sanghuang mushroom, is a medicinal mushroom that has been recognized as beneficial to health for more thousands of years. Among its diverse valuable secondary metabolites, the yellow‐brown styrylpyrone pigment hispidin has garnered significant attention due to its various pharmacological effects. However, recently after detailed morphological and molecular phylogenetic studies, the correct scientific name of the true sanghuang strains was shown not to be P. linteus but Sanghuangporus sanghuang. As the incorrect binomial name P. linteus has long been misleadingly referred, there is a need to evaluate the safety of S. sanghuang. Moreover, the growing conditions can impact the secondary metabolite profile of the fungi. Hence, this study is the first to optimize hispidin production and to investigate the genotoxic and oral toxic effects of hispidin‐enriched S. sanghuang mycelia. In order to induce the biosynthesis of hispidin, 15 different culture media consisting of five carbon sources, five nitrogen sources, and five initial pH conditions were screened. Glucose and yeast extract at an initial pH of 5 were found to be the most suitable carbon and nitrogen sources, respectively, for the optimal growth and production of hispidin. Moreover, the production of hispidin was 3 mg/g in a 20‐ton bioreactor under optimal conditions. Furthermore, the ames test, in vitro chromosome aberration test, acute oral toxicity test, and bone marrow micronucleus test were used to detect toxicological properties of 3 mg/g hispidin‐enriched S. sanghuang mycelia. In all tests, there was no statistically significant difference between the mycelia and the negative control. Based on the results obtained, the present study demonstrates that 3 mg/g hispidin‐enriched S. sanghuang mycelia has a very low order of toxicity, which supports its safety for human consumption.

Long-term alkaline conditions inhibit the relative abundances of tetracycline resistance genes in saline 4-chlorophenol wastewater treatment

Considering the occurrence and spread of antibiotic resistance genes (ARGs) pose significant risks to public health, the effects of long-term exposure to alkaline conditions on the relative abundances of tetracycline resistance genes (TRGs) were studied in saline 4-chlorophenol (4-CP) wastewater treatment. Alkaline conditions were maintained by supplying the co-metabolic carbon source of sodium acetate. Results showed that except for the 4-CP, the removal of pollutants was significantly inhibited, and the relative abundances of the most TRGs were repressed. In addition, the removal of pollutants and the relative abundances of TRGs were moderately affected by the NaCl addition. The proteins in the extracellular polymeric substances (EPS) played key roles in reducing the relative abundances of TRGs, which were altered by the microbial diversity. In conclusion, for the pollutants removal and ARGs reduction in refractory industrial wastewater treatment, alkaline conditions should be maintained by selecting suitable co-metabolic carbon sources.

Production and characterization of polyhydroxyalkanoates synthesized by E. coli Isolated from sludge soil

The petrochemical-based non-degradative polymers are causing severe environmental pollution that resulting in acute or chronic toxicity in living organisms. Hence emerging of biological polymers is significant to replace traditional polymers. Therefore, the present study aimed to isolate efficient PHAs producing bacteria from municipal sludge soil, characterize the biopolymers by FT-IR and 1H NMR and optimize growth conditions for mass production of PHAs. 10 predominant bacteria cultures were isolated from sludge soil, out of 10 single isolates has the potential to produce PHAs, and it was characterized and identified asE. coli.The PHAs produced byE. coliwas characterized by FT-IR and NMR analysis. The results show that components of PHAs such as carbonylhydroxybutyrate, hydroxyoctaoate (HO), medium chain length polyhydroxyalkanoates, and hydroxydecanoate showed their strong characteristic band at 1631 cm−1, 1548 cm−1, 1409 cm-1 respectively in the extracted sample. Further, the NMR reports show that the presence of interconnection functional groups like HC = CH bond at 3.363 ppm, CH2O–COOH bond at 2.548 ppm. The optimal growth conditions forE. coliwere optimized. Briefly, 9% of inoculum, sago molasses (as suitable carbon source), 35 °C, pH 7.5 48hrs of incubation, in which theE. coliproduce 27.1 g/L of PHAs extracted from 33.26 g/L of biomass and in percentage it was calculated as 81.47%. The entire results determine that the E. colienumerated from sludge soil has the efficiency to produce PHAs, hence it possible for commercialization by using cheap carbon sources.

Screening and optimization of exopolysaccharide producing bacteria from rhizospheric region of direct seeded rice

Exopolysaccharide (EPS) are are high molecular weight substances mainly comprise of polysaccharides but also contains non- sugar components like protein, nucleic acid and lipids which mainly originated from microbial origin. With the rising awareness of microbial EPS in various fields, rice rhizospheric microorganisms received broad attention and play a crucial role in protecting crops during the stress condition. The present study was to obtained exopolysaccharide producing bacteria from direct seeded rice. Soil samples were collected from rice rhizospheric region (0-15cm depth). Thirty-seven organisms were isolated from rhizosheric region of direct seeded rice and identified by morphological, biochemical and microscopic analysis. Out of thirty-seven isolates eighteen isolates produced mucoid substances and having gram -ve in nature. After screening with Polyethylene glycol (PEG-6000), six isolates tolerate maximum level of stress (-0.73MPa). The production of six isolates were ranged from 3.4 to 5.5g/l. The potential six isolates were optimized with temperature, pH, incubation period, Salt concentration and carbon source. We found that, 37 0C and 7.5 pH were optimum for EPS production. The production rate was decreased with increasing pH and salt concentration. Sucrose was the suitable carbon source for production of EPS. The finding of the study imply the isolates have potential to produce EPS from rice rhizosperic region. Further study should aim to molecular identification and EPS linking with drought tolerance and water use efficiency under direct seeded rice.

Nghiên cứu ương ấu trùng tôm chân trắng (Litopenaeus vannamei) theo công nghệ biofioc với các nguồn carbon bổ sung khác nhau

The aim of this study was to identify suitable carbon sources for the growth and survival of larvae of white-leg shrimp nursed in tanks with biofloc technology. The experiment was conducted with five treatments: (i) no carbon supplement (control), (ii) carbon supplement from wheat flour, (iii) carbon supplement from rice bran, (iv) carbon supplement from wheat and rice bran at a ratio of 50:50 and (v) carbon supplement from sugar. Each treatment was triplicated. The experimental tank was 500 liters in volume. Stocking density was 150 larvae/liter and water salinity was 30‰. Results of the experiment showed that the body length of 12-day old postlarvae (PL12) in the sugar treatment (10.18±0.15mm) was the highest and significantly different (p0.05) compared to the other treatments. The survival rate (52±5.1%) and productivity (78±8 larvae/liter) of PL12 in the sugar treatment were also the highest and significantly different (p

Effect of Carbon Source on Properties and Bioactivities of Exopolysaccharide Produced by Trametes ochracea (Agaricomycetes).

The effects of carbon source on properties and bioactivities of exopolysaccharide (EPS) produced by Trametes ochracea were investigated in this study. The results indicated that EPS production varied with five different carbon sources. After a fermentation period of 8 days, sucrose was the most suitable carbon source for biomass and EPS production. The predominant carbohydrate compositions in EPSs identified were glucose and mannose. The EPS fermented by sucrose has the highest glucose content. Then, FT-IR spectral analysis revealed prominent characteristic groups in EPSs. Each particular EPS possessed the specific bands at 808-809 cm-1 and 914-922 cm-1, indicating both α- and β-configurations of the sugar units. Furthermore, thermogravimetric analysis (TGA) indicated the EPS with sucrose and glucose as carbon source showed different degradation behavior compared with the other three EPSs. The variation also affects antioxidant and antihyperlipemia activities investigated using hydroxyl and DPPH radical scavenging assay, and in hyperlipemia mice. Sucrose was the best carbon source from the viewpoint of OH and DPPH radical scavenging activities, and antihyperlipemia activity, probably due to the relatively high glucose content in EPS.

Preliminary Characterization of Exopolysaccharides Produced by Abortiporus biennis in Submerged Fermentation

Abortiporus biennis is a rare edible and medicinal mushroom that is valuable in traditional Chinese medicine. Exopolysaccharides (EPSs) as valuable metabolites have been harvested from fermentation broths of A. biennis. However, studies on preliminary characterisations and bioactivities of A. biennis EPSs are lacking. In this study, therefore, the production, characteristics and bioactivity of EPSs produced by A. biennis in submerged fermentation were investigated. An EPS-1 was isolated and purified from the culture broth of A. biennis using a Sepharose CL-6B column chromatography. The molecular weight, monosaccharide composition, structural characteristics, chain conformation and thermal property of EPS-1 were determined by gel-filtration chromatography, gas chromatography-mass spectroscopy, Fourier-transform infrared spectroscopy, Congo red test and thermogravimetric analysis, respectively. The in vitro antioxidant and immunoregulation activities of the EPS-1 were evaluated by adopting DPPH and hydroxyl radical-scavenging assays, and analysing NO production in macrophage RAW 264.7 cells, respectively. Results showed that the culture medium containing 30 g/L lactose and 3.0 g/L tryptone had the most suitable carbon and nitrogen sources, respectively, for EPS production in A. biennis. The maximum EPS production (18.29 g/L) was obtained after 6 days of cultivation in a 5 L stirred-tank reactor under the most suitable culture medium. After purification, EPS-1 with 85.4% yield and 96.1% carbohydrate content was obtained from the culture broth of A. biennis. EPS-1 was characterised as a neutral heteropolysaccharide with a molecular weight of 22.07 kDa and is composed of glucose, mannose and galactose at a molar ratio of 3.3:2.0:1.0. EPS-1 with a relatively high thermal stability existed as a random coil conformation in the aqueous medium and possessed prominent radical-scavenging ability and macrophage stimulation activity in vitro. Therefore, EPS-1 could be explored as a functional ingredient with potential applications in food, medical and cosmetic industries.

Characterization and optimization of production of bacterial cellulose from strain CGMCC 17276 based on whole-genome analysis

Bacterial cellulose (BC) has received considerable attention as an environment-friendly, biodegradable nanomaterial. In this study, the strain Komagataeibacter sp. nov. CGMCC 17276, which showed rapid cell growth and high BC-production ability, was isolated and classified into a novel species in the Komagataeibacter genus. Four BC synthase operons were annotated using whole-genome analysis, partially explaining the high BC yield of strain CGMCC 17276. Operons bcs Ⅱ and bcs Ⅲ showed high transcriptional levels under static and agitated culture conditions, indicating their importance in BC synthesis. Of the eight suitable carbon sources identified by whole-genome analysis, the highest BC production was achieved using glycerol as a single carbon source. Finally, waste glycerol was successfully used as an eco-friendly and sustainable strategy for BC production. This study provides valuable insights into the mechanism of BC synthesis, genetic structure of BC-producing strains, and industrialization of BC production using an eco-friendly and low-cost strategy.

RSM-GA Based Optimization of Bacterial PHA Production and In Silico Modulation of Citrate Synthase for Enhancing PHA Production.

The inexhaustible nature and biodegradability of bioplastics like polyhydroxyalkanoates (PHAs) make them suitable assets to replace synthetic plastics. The eventual fate of these eco-friendly and non-toxic bioplastics relies upon the endeavors towards satisfying cost and, in addition, execution necessity. In this study, we utilized and statistically optimized different food (kitchen-/agro-) waste as a sole carbon/nitrogen source for the production of PHA at a reduced cost, indicating a proficient waste administration procedure. Seven different types of kitchen-/agro-waste were used as unique carbon source and four different types of nitrogen source were used to study their impact on PHA production by Bacillus subtilis MTCC 144. Among four different studied production media, mineral salt medium (MSM) (biomass: 37.7 g/L; cell dry weight: 1.8 g/L; and PHA: 1.54 g/L) was found most suitable for PHA production. Further, carbon and nitrogen components of MSM were optimized using one-factor-at-a-time experiments, and found that watermelon rind (PHA = 12.97 g/L) and pulse peel (PHA = 13.5 g/L) were the most suitable carbon and nitrogen sources, respectively, in terms of PHA (78.60%) recovery. The concentrations of these factors (sources) were statistically optimized using response surface methodology coupled with the genetic algorithm approach. Additionally, in order to enhance microbial PHA production, the interaction of citrate synthase, a key enzyme in the TCA cycle, with different known inhibitors was studied using in silico molecular docking approach. The inhibition of citrate synthase induces the blockage of the tricarboxylic cycle (TCA), thereby increasing the concentration of acetyl-CoA that helps in enhanced PHA production. Molecular docking of citrate synthase with different inhibitors of PubChem database revealed that hesperidin (PubChem compound CID ID 10621), generally present in citrus fruits, is the most efficient inhibitor of the TCA cycle with the binding score of –11.4 and warrants experimental validation. Overall, this study provides an efficient food waste management approach by reducing the production cost and enhancing the production of PHA, thereby lessening our reliance on petroleum-based plastics.

Three-dimensional porous pitch-derived carbon coated Si nanoparticles-CNT composite microsphere with superior electrochemical performance for lithium ion batteries

Although silicon has attracted attention as a promising anode material for lithium ion batteries due to its high theoretical capacity and relatively low discharge potential, the issue of large volume expansion and contraction during its de-/alloying reaction with Li has resulted in the development of nanostructured electrode design and coating methods using suitable carbon sources to improve the stability of the electrode. Pitch is regarded as an attractive carbon coating source owing to its mesophase characteristics, high mechanical strength, and electrical conductivity. In this study, three-dimensional porous pitch-derived carbon coated Si nanoparticles-carbon nanotube (Si-CNT@PC) composite microspheres were successfully synthesized by spray pyrolysis and a following pitch infiltration process. Uniformly distributed Si nanoparticles, acid-treated multiwall CNTs, and polystyrene (PS) nanobeads enabled the formation of porous structured Si-CNT composite microspheres by spray pyrolysis. Uniform infiltration of pitch dissolved in tetrahydrofuran followed by a carbonization process resulted in Si-CNT@PC microspheres. The uniquely structured Si-CNT@PC microspheres exhibited superior electrochemical properties compared with Si-CNT microspheres not coated with carbon. The synergetic effects of carbon-coated Si nanoparticles, macroporous structure formed by decomposition of PS nanobeads, and the CNT backbone resulted in excellent lithium-ion storage performance of Si-CNT@PC microspheres. The discharge capacities of Si-CNT and Si-CNT@PC at a current density of 1 A g−1 for the 200th cycle were 51 and 1209 mA h g−1, respectively.

Biomass and phycocyanin content of heterotrophic Galdieria sulphuraria 074G under maltodextrin and granular starches\u2013feeding conditions

A major disadvantage of microalgal cultivation is limited biomass yields due to the autotrophic lifestyle of most microalgal species. Heterotrophic growth on a suitable carbon source and oxygen can overcome such limitations. The red microalga Galdieria sulphuraria strain 074G grows heterotrophically on glucose and a number of other carbon sources while constitutively producing photopigments, including the blue-colored phycocyanin, a natural food colorant. Galdieria sulphuraria strain 074G grew well on maltodextrins as well as on granular starch in combination with the enzyme cocktail Stargen002. The maltodextrin cultures produced 2 mg phycocyanin per gram substrate, being slightly more than on glucose. The phycocyanin extracted from maltodextrin-grown cultures was thermostable up to 55 °C. Maltodextrins can be a cheap alternative to glucose syrups for the production of phycocyanin as natural food colorant.

Determining a suitable carbon source for the production of intracellular pigments from Monascus purpureus HBSD 08

Purpose The Monascus pigment has been widely applied in the food processing industry as a functional additive. Lovastatin and polysaccharides are two important bio-active materials found in Monascus. Citrinin is considered as mycotoxin. Thus, it is important to produce high yields of intracellular Monascus pigments with high yields of lovastatin and polysaccharides, while maintaining low citrinin yields under liquid fermentation. Design/methodology/approach The intracellular yields of pigments, lovastatin, polysaccharides and citrinin; biomass; and reducing the sugar content of Monascus purpureus HBSD 08 were determined every day during a 10-day culturing period using lactose, maltose, sucrose, glucose, glycerine and xylose as the sole carbon sources. Additionally, the pigment composition was analysed by a thin layer chromatography (TLC) and the in vitro antitumor activities of the pigments were determined. Findings The maximal yield of pigments (55.44 U/mL after six days of culture) and lovastatin content (1,475.30 µg/L after five days of culture) were obtained in the presence of glucose and maltose as the sole carbon sources, respectively. The suitable carbon sources for high intracellular polysaccharides yields were sucrose, maltose and xylose. Glucose should not be chosen as the sole carbon source because of its high food safety risk. In vitro antitumor activities of pigments in the presence of different carbon sources were in the order of xylose > glucose = maltose > glycerine > sucrose = lactose. The pigment compositions in the presence of different carbon sources were the same from the TLC analysis. Thus, maltose displayed high intracellular yields of pigments, lovastatin and polysaccharides; high food safety against citrinin, and high in vitro antitumor activity during the ten days culturing period. Originality/value This study shows us the benefits of using maltose as a substrate in the production of intracellular Monascus pigments while ensuring economic and food safety.

Soil Microbial Communities Involved in Reductive Dissolution of Arsenic from Arsenate-Laden Minerals with Different Carbon Sources.

The natural microbial communities involved in arsenic (As) extraction under biostimulated conditions are still unclear. In this study, soil slurry was incubated with arsenate [As(V)]-laden Fe(III) or Al (hydr)oxides with lactate or acetate. After 40 d, dissolved As released from As(V)-laden Fe(III) accounted for 54% of the initial solid-phase As in lactate-amended slurries, while much less As was released from acetate-amended slurries. As was released more rapidly from As(V)-laden Al, but the total release was relatively low (45%). High-throughput Illumina sequencing of 16S rRNA genes revealed that dissimilatory metal(loid) reducers such as Desulfitobacterium became predominant in lactate-amended slurries. Moreover, anaerobic fermenters in the Sporomusaceae family were predominant. Interestingly, a Sporomusaceae bacterial strain isolated from the slurry was capable of releasing As from both As(V)-laden (hydr)oxides in the presence of lactate. The strain first released As as As(V) and subsequently reduced it to As(III) in the aqueous phase. These results suggest that lactate is a suitable carbon source for As extraction by natural microbial communities, and that both dissimilatory metal(loid) reducers and certain anaerobic fermenters play significant roles in As extraction. Microbial reductive dissolution of As may be expected to be a cost-effective restoration technique for As-contaminated soils.

Levan production from sucrose using chicken feather peptone as a low cost supplemental nutrient source

Chicken feather peptone (CFP) derived from poultry waste is a rich source of essential minerals and amino acids. This, along with suitable carbon source, can be used as a low cost complex supplemental nutrient source for microbial fermentation. In the present work, CFP blended with sucrose was evaluated for the production of levan using Bacillus subtilis MTCC 441. Amount of CFP added to the medium significantly influenced levan production and it was found that at a concentration 2 g/L, maximum levan yield of 0.26 ± 0.04 g/g sucrose was obtained. The levan yield obtained with CFP as a low cost supplemental nutrient source was comparable with that obtained from commercial medium (0.31 ± 0.02 g/g sucrose). Levan produced using CFP was tested on primary cell lines at various concentrations (100–1000 μM) and found to be non-toxic and bio-compatible in nature. This indicates that CFP could be used as low cost nutrient source for levan production.

Suitable carbon sources selection and ranking for biodiesel production by oleaginous Mucor circinelloides using multi-criteria analysis approach

Crude oil is the most important raw material used in chemical industry and for energy supply. Microbial lipids are ideal for various industrial applications as an alternative to conventional fuel. However, the main factor controlling the total production costs is the choice of the growth substrates. For this reason, economically feasible substrate such as agro-industrial residues has been explored. In addition, the most suitable substrates for biodiesel production were selected by PROMETHEE-GAIA analysis on the basis of the fatty acid profile of the produced oils. Six strains were selected as the best lipid producer among twenty-three fungal strains screened by colorimetric methods. The strains identified belong to the genera Fusarium and Mucor. Mucor circinelloides was chosen for comparative evaluation of the accumulation performance with different carbon sources. The use of soap stock of refined soybean oil, waste cooking oils and soap stock of refined olive-pomace successfully resulted in improved lipid yield (4.07, 2.69 and 2.44 g/L) (ρ = 0.001; ρ > 0.05) and the lipid content at 46%, 51% and 44% (ρ = 0.049; ρ < 0.05) respectively. The ability to use low-cost agro industrial raw materials for the production of microbial lipids has been proven. The fatty acid profile of M. circinelloides grown on used cooking oils improved the level of linoleic acid (56.26%) that can be valorized as additive in health and dietary supplements. Glucose, refined olive-pomace oil soap stock, and refined soybean oil have influenced the resulting fatty acid profile and meet the characteristics required for successful biodiesel production.

Optimization and characterization of bacterial cellulose produced by Komagatacibacter xylinus PTCC 1734 using vinasse as a cheap cultivation medium

In the present study, vinasse was used to produce bacterial cellulose (BC) by Komagatacibacter xylinus PTCC 1734. Central composite design (CCD) was utilized to evaluate the effects of vinasse concentration (%) and incubation time (Day) on different responses such as thickness as well as wet and dry weights of the produced BC membrane. The increase of vinasse concentration and incubation time caused an increase in the wet weight of BC; however, thickness decreased by increasing incubation time. The BC produced at the optimized conditions (40% vinasse and 10 days) was characterized and compared with the BC produced in Hestrin-Schramm medium as a control medium. Scanning electron microscopy (SEM) confirmed 3D network structure of BC. The average diameter of fibrils was in the range of 30–120 nm. In addition, the Fourier transform infrared spectroscopy (FT-IR) showed completely similar spectrum for both optimal and control samples. The X-ray diffraction (XRD) analysis approved the crystalline structure of the produced BC. Furthermore, the thermogravimetric analysis (TGA) test revealed no difference in the thermal stability of the optimum and control sample. According to the results, the vinasse, as a by-product, could be used as a cheap and suitable carbon source for the production of BC.

Catalytic, kinetic and thermodynamic properties of free and immobilized caseinase on mica glass-ceramics

Bacillus megaterium 314 strain was able to utilize agricultural and industrial wastes for metallo-protease production. Orange peel and wheat bran were found as the most suitable carbon and nitrogen sources, respectively. Optimized production process enhanced the enzyme production by 5.1-folds. Glass and glass-ceramic with different particle sizes based on mica were used as inorganic carrier. Protease enzyme was immobilized by covalent bonding and physical adsorption methods on nanoparticle supports. Enzyme physically adsorbed on glass ceramic (particle size 0.71–1.0 mm) had the highest residual activity and the highest immobilization yield. Glass-ceramic was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Immobilized enzyme exhibited activation energy (Ea) and deactivation rate constant at 60 °C (kd) about 1.29 and 1.46-times, respectively lower than free enzyme. Moreover, adsorbed enzyme had higher energy for denaturation (Ed), half-life (t1/2), and decimal reduction time (D). The thermodynamic parameters of irreversible thermal denaturation for the protease enzyme indicate that immobilized enzyme had higher enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°) than free one. There was a significant improvement in the maximum reaction velocity Vmax (2.5-fold), Michaelis constant Km (1.9-fold), and catalytic efficiency Vmax/Km (4.7-fold) values after immobilization indicating the efficiency and effectiveness of immobilization approach.

OPTIMIZATION OF MEDIUM COMPONENTS FOR THE PRODUCTION OF ECTOINE BY A HALOPHILIC BACTERIUM ISOLATED FROM CAN GIO MANGROVE

The effect of different carbon and nitrogen sources on growth of producer strain was investigated. Sucrose and glucose were found to be suitable carbon sources, and monosodium glutamate was favorable nitrogen source for bacterial cell growth. Optimum salt concentrations for bacterial growth was ranged from 4 to 6%, whereas, NaCl concentrations from 12 to 15% found to be good for ectoine accumulation. Two-step fed-batch fermentation was then designed, biomass and ectoine content were significant increased, maximum CDW of 25 g/l and ectoine content of 10.3% were obtained.