Production of <Emphasis Type="Italic">R</Emphasis>-Mandelic Acid Using Nitrilase from Recombinant <Emphasis Type="Italic">E. coli</Emphasis> Cells Immobilized with Tris(Hydroxymethyl)Phosphine

Recombinant Escherichia coli cells harboring nitrilase from Alcaligenes faecalis were immobilized using tris(hydroxymethyl)phosphine (THP) as the coupling agent. The optimal pH and temperature of the THP-immobilized cells were determined at pH 8.0 and 55 °C. The half-lives of THP-immobilized cells measured at 35, 40, and 50 °C were 1800, 965, and 163 h, respectively. The concentration of R-mandelic acid (R-MA) reached 358 mM after merely 1-h conversion by the immobilized cells with 500 mM R,S-mandelonitrile (R,S-MN), affording the highest productivity of 1307 g L^?1 day^?1 and the space-time productivity of 143.2 mmol L^?1 h^?1 g^?1. The immobilized cells with granular shape were successfully recycled for 60 batches using 100 mM R,S-MN as substrate at 40 °C with 64% of relative activity, suggesting that the immobilized E. coli cells obtained in this study are promising for the production of R-MA.     

Growth of Cyanobacteria: Optimization for Increased Carbohydrate Content

Growths of Lyngbya limnetica and Oscillatoria obscura were investigated at varying pH, light intensity, temperature, and trace element concentration with a view to optimize these parameters for obtaining the maximum carbohydrate content. The maximum growth for both strains was obtained at pH 9.0 and temperature 20 ± 3 °C using a light intensity of 68.0 μmol m^?2 s^?1 with continuous shaking. Growth under the nitrogen starvation condition affected the carbohydrate content more compared to the phosphorus starvation, and maximum concentrations were found as 0.660 and 0.621 g/g of dry biomass for L. limnetica and O. obscura, respectively. Under the optimized nitrogen-rich conditions, the specific growth rates for the two strains were found to be 0.187 and 0.215 day^?1, respectively. The two-stage growth studies under nitrogen-rich (stage I) followed by nitrogen starvation (stage II) conditions were performed, and maximum biomass and carbohydrate productivity were found as 0.088 and 0.423 g L^?1 day^?1 for L. limnetica. This is the first ever attempt to evaluate and optimize various parameters affecting the growth of cyanobacterial biomass of L. limnetica and O. obscura as well as their carbohydrate contents.     

Single-cell Protein and Xylitol Production by a Novel Yeast Strain <Emphasis Type="Italic">Candida intermedia</Emphasis> FL023 from Lignocellulosic Hydrolysates and Xylose

Yeasts are good candidates to utilize the hydrolysates of lignocellulose, the most abundant bioresource, for bioproducts. This study aimed to evaluate the efficiencies of single-cell protein (SCP) and xylitol production by a novel yeast strain, Candida intermedia FL023, from lignocellulosic hydrolysates and xylose. This strain efficiently assimilated hexose, pentose, and cellubiose for cell mass production with the crude protein content of 484.2 g kg^?1 dry cell mass. SCP was produced by strain FL023 using corncob hydrolysate and urea as the carbon and nitrogen sources with the dry cell mass productivity 0.86 g L^?1 h^?1 and the yield of 0.40 g g^?1 sugar. SCP was also produced using NaOH-pretreated Miscanthus sinensis straw and corn steep liquor as the carbon and nitrogen sources through simultaneous saccharification and fermentation with the dry cell productivity of 0.23 g L^?1 h^?1 and yield of 0.17 g g^?1 straw. C. intermedia FL023 was tolerant to 0.5 g L^?1 furfural, acetic acid, and syringaldehyde in xylitol fermentation and produced 45.7 g L^?1 xylitol from xylose with the productivity of 0.38 g L^?1 h^?1 and the yield of 0.57 g g^?1 xylose. This study provides feasible methods for feed and food additive production from the abundant lignocellulosic bioresources.     

Growth Parameters,Photosynthetic Performance,and Biochemical Characterization of Newly Isolated Green Microalgae in Response to Culture Condition Variations

This work aimed to characterize two native microalgal strains newly isolated from South Mediterranean areas and identified as Chlorella sorokiniana ES3 and Neochloris sp. AM2. The growth properties and biochemical composition of these microalgae were evaluated in different culture media (Algal, BG-11, f/2, and Conway). Among the tested media, nitrate- and phosphate-rich Algal medium provided the maximum biomass productivities (85.5 and 111.5 mg l^?1 day^?1 for C. sorokiniana and Neochloris sp., respectively), while the nitrate- and phosphate-deficient f/2 medium resulted in the highest lipid productivities (24.1 and 35.8 mg l^?1 day^?1 for C. sorokiniana and Neochloris sp., respectively). The physiological state of both microalgae was investigated under different light and temperature levels using the pulse amplitude-modulated fluorometry. The better photosynthetic efficiency of C. sorokiniana was obtained at 23 °C with a light saturation of 156 μE m^?2 s^?1, while that of Neochloris sp. was achieved at 15 °C with a light saturation of 151 μE m^?2 s^?1. The analysis of fatty acid profile and biodiesel parameters revealed that C. sorokiniana, cultivated in Algal and f/2 media, can be considered as a suitable candidate for high-quality biodiesel production.     

Characterization of Truncated <Emphasis Type="Italic">dsz</Emphasis> Operon Responsible for Dibenzothiophene Biodesulfurization in <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. FUM94

Numerous desulfurizing bacteria from the Rhodococcus genus harbor conserved dsz genes responsible for the degradation of sulfur compounds through 4S pathway. This study describes a newly identified desulfurizing bacterium, Rhodococcus sp. FUM94, which unlike previously identified strains encodes a truncated dsz operon. DNA sequencing revealed a frameshift mutation in the dszA gene, which led to an alteration of 66 amino acids and deletion of other C-terminal 66 amino acids. The resulting DszA polypeptide was shorter than DszA in Rhodococcus sp. IGTS8 reference strain. Despite the truncation, desulfurizing activity of the operon was observed and attributed to the removal of an overlap of dszA and dszB genes, and lack of active site in the altered region. Desulfurization experiments resulted in specific production rate of 6.3 mmol 2-hydroxy biphenyl (kgDCW)^?1 h^?1 at 2 g l^?1 biocatalyst concentration and 68.8% biodesulfurization yield at 20 g l^?1 biocatalyst concentration, both at 271 μM dibenzothiophene concentration which is comparable to similar wild-type biocatalysts.     

Synthesis,antifungal and insecticidal activity of novel [1,2,4]triazolo[4,3-<Emphasis Type="Italic">a</Emphasis>]pyridine derivatives containing a sulfide substructure

A series of [1,2,4]triazolo[4,3-a]pyridine derivatives bearing a sulfide substructure was designed, synthesized and characterized via ¹H·NMR, ¹³C·NMR, IR and elemental analyses. Bioassay Results indicated some of the derivatives displayed good fungicidal activity on Rhizoctonia cerealis, moderated insecticidal activity against Plutella xylostella and good insecticidal activity on Helicoverpa armigera. The inhibitory effects of compounds 4g and 4u against Rhizotonia cerealis were 70.9% at 50 μg mL^?1; the IC₅₀ values of compounds 4d and 4s against Plutella xylostella were 43.87 and 50.75 μg mL^?1, respectively. And the IC₅₀ values of compounds 4d, 4q, and 4s on Helicoverpa armigera were 58.3, 77.14 and 65.31 μg mL^?1, respectively, which were better than that of commercial chlorpyrifos (103.77 μg mL^?1).     

<Emphasis Type="Italic">cis</Emphasis>-Dioxomolybdenum(VI) complexes of sterically encumbered phenol-based tetradentate N<Subscript>2</Subscript>O<Subscript>2</Subscript> ligands: Structural,spectroscopic, and electrochemical studies

Two cis-dioxomolybdenum(VI) complexes [MoO₂L] (L: L ¹, 2 and L: L ², 3) in a phenol-based sterically encumbered N₂O₂ ligand environment have been synthesized, and their crystallographic characterizations are reported. The orange crystals of 2 are monoclinic, space group P2₁/a with unit cell dimensions as a=16.2407(17) Å, b=7.2857(8) Å, c=18.400(2) Å, β=98.002(9)°, Z=4, and d _cal=1.486 g cm^?3. The light orange crystals of 3, however, are orthorhombic, space group, Pbcn, with unit cell dimensions a=8.3110(12) Å, b=12.637(3) Å, c=34.673(5) Å, Z=4, and d _cal=1.187 g cm^?3. The structures were refined by a full-matrix least-squares procedure on F ² to a final R=0.046 (0.055 for 3) using 4944 (3677) all independent data. In both the cases, the Mo atom exists in a distorted octahedral geometry defined by a N₂O₄ donor set, which features a cis-Mo(–O)₂ and a trans-Mo(OPh)₂ arrangement. Compound 2 undergoes a quasireversible one-electron reduction at ?1.3 V vs Ag/AgCl reference due to Mo^VIO₂/Mo^VO₂ electron transfer and thus providing a rare example of steric solution to the comproportionation–dimerization problem encountered frequently in the development of valid biomimetic models for the active sites of oxomolybdenum enzymes.     

Enhanced Production of Xylitol from Poplar Wood Hydrolysates Through a Sustainable Process Using Immobilized New Strain <Emphasis Type="Italic">Candida tropicalis</Emphasis> UFMG BX 12-a

A new strain, Candida tropicalis UFMG BX 12-a, was found to produce higher yields of xylitol on poplar wood hemicellulose hydrolysate. The hemicellulose hydrolysate liquor was detoxified using a novel method we developed, involving vacuum evaporation and solvent separation of inhibitors which made the hydrolysate free of toxins while retaining high concentrations of fermentable sugars. The effect of the detoxification method on the fermentation was also reported and compared to well-known methods reported in literature. In this study, the new strain C. tropicalis UFMG BX 12-a was used on the detoxified hydrolysate to produce xylitol. It was also compared to Candida guilliermondii FTI 20037, which has been reported to be one of the best strains for fermentative production of xylitol. To further improve the efficiency of the fermentation process, these strains were immobilized in calcium alginate beads. The yield (0.92 g g^?1) and productivity (0.88 g L^?1 h^?1) obtained by fermenting the wood hydrolysate detoxified by our new detoxification technique using an immobilized new Candida strain were found to be higher than the values reported in literature.     

Efficient Biotransformation of Phytosterols to Dehydroepiandrosterone by <Emphasis Type="Italic">Mycobacterium</Emphasis> sp.

In this study, a method for the efficient production of dehydroepiandrosterone (DHEA) from phytosterols in a vegetable oil/aqueous two-phase system by Mycobacterium sp. was developed. After the 3-hydroxyl group of phytosterols was protected, they could be converted into DHEA with high yield and productivity by Mycobacterium sp. NRRL B-3683. In a shake flask biotransformation, 15.05 g l^?1 of DHEA and a DHEA yield of 85.39% (mol mol^?1) were attained after 7 days with an initial substrate concentration of 25 g l^?1. When biotransformation was carried out in a 30-l stirred bioreactor with 25 g l^?1 substrate, the DHEA concentration and yield was 16.33 g l^?1 and 92.65% (mol mol^?1) after 7 days, respectively. The results of this study suggest that inexpensive phytosterols could be utilized for the efficient production of DHEA.     

Co-production of Fructooligosaccharides and Levan by Levansucrase from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> natto with Potential Application in the Food Industry

Fructooligosaccharides and levan have a wide range of applications in the food industry due to their physiological and functional properties. The enzymatic synthesis of these molecules exhibits great advantages when compared with microbial fermentation. In this study, the production of levansucrase from Bacillus subtilis natto and its utilization in fructooligosaccharides and levan syntheses using different reaction conditions were described. The best condition for levansucrase production was 420.7 g L^?1 of sucrose at pH 7.0, which reached 23.9 U ml^?1 of transfructosylation activity. In a bioreactor, the highest production of fructooligosaccharides was 41.3 g L^?1 using a medium containing 350 g L^?1 sucrose at 35 °C for 36 h. The enzymatic synthesis of levan resulted in 86.9 g L^?1 when conditions similar to those used for fructooligosaccharides synthesis were applied. These results indicate that the levansucrase from B. subtilis natto could be applied for the co-production of fructooligosaccharides and levan, which are biomolecules that have health benefits and are used successfully in the food industry.     

Highly Efficient Deracemization of Racemic 2-Hydroxy Acids in a Three-Enzyme Co-Expression System Using a Novel Ketoacid Reductase

Enantiopure 2-hydroxy acids (2-HAs) are important intermediates for the synthesis of pharmaceuticals and fine chemicals. Deracemization of racemic 2-HAs into the corresponding single enantiomers represents an economical and highly efficient approach for synthesizing chiral 2-HAs in industry. In this work, a novel ketoacid reductase from Leuconostoc lactis (LlKAR) with higher activity and substrate tolerance towards aromatic α-ketoacids was discovered by genome mining, and then its enzymatic properties were characterized. Accordingly, an engineered Escherichia coli (HADH-LlKAR-GDH) co-expressing 2-hydroxyacid dehydrogenase, LlKAR, and glucose dehydrogenase was constructed for efficient deracemization of racemic 2-HAs. Most of the racemic 2-HAs were deracemized to their (R)-isomers at high yields and enantiomeric purity. In the case of racemic 2-chloromandelic acid, as much as 300 mM of substrate was completely transformed into the optically pure (R)-2-chloromandelic acid (>?99% enantiomeric excess) with a high productivity of 83.8 g L^?1 day^?1 without addition of exogenous cofactor, which make this novel whole-cell biocatalyst more promising and competitive in practical application.     

Xanthan Gum Production by <Emphasis Type="Italic">Xanthomonas campestris pv. campestris</Emphasis> IBSBF 1866 and 1867 from Lignocellulosic Agroindustrial Wastes

This study aimed to evaluate the properties of xanthan gum produced by Xanthomonas campestris pv. campestris 1866 and 1867 from lignocellulosic agroindustrial wastes. XG was produced using an orbital shaker in a culture medium containing coconut shell (CS), cocoa husks (CH), or sucrose (S) minimally supplemented with urea and potassium. The XG production results varied between the CS, CH, and S means, and it was higher with the CH in strains 1866 (4.48 g L^?1) and 1867 (3.89 g L^?1). However, there was more apparent viscosity in the S gum (181.88 mPas) and the CS gum (112.06 mPas) for both 1866 and 1867, respectively. The ability of XG_CS and XG_CH to emulsify different vegetable oils was similar to the ability of XG_S. All gums exhibited good thermal stability and marked groups in the elucidation of compounds and particles with rough surfaces.     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

Application of Physicochemical Treatment Allows Reutilization of <Emphasis Type="Italic">Arthrospira platensis</Emphasis> Exhausted Medium

Since cultivations of Arthrospira platensis have a high water demand, it is necessary to develop treatment methods for reusing the exhausted medium that may prevent environmental problems and obtaining useful biomass. The exhausted Schlösser medium obtained from A. platensis batch cultivation in bench-scale mini-tanks was treated by varying concentrations of different coagulants, ferric chloride (6, 10, and 14 mg L^?1) or ferric sulfate (15, 25, and 35 mg L^?1) and powdered activated carbon (PAC, 30 and 50 mg L^?1). Such treated effluent was restored with NaNO₃ and reused in new cultivations of A. platensis performed in Erlenmeyer flasks. Reusing media through the cultivation of A. platensis showed satisfactory results, particularly in the medium treated with ferric chloride and PAC. The maximum cell concentration obtained in the flasks was 1093 mg L^?1, which corresponded to the medium treated with ferric chloride (6 mg L^?1) and PAC (30 mg L^?1). This cellular growth was higher than in the medium treated with ferric sulfate and PAC, in which values of maximum cell concentration did not exceed 796 mg L^?1. The cultures in the media after treatment did not modify the biomass composition. Thus, combined coagulation/adsorption processes, commonly used in water treatment processes, can be efficient and viable for treating exhausted medium of A. platensis, allowing the production of such biomass with the reduction of production cost and saving water.     

Synthesis,crystal structure,and thermodynamics of a high-nitrogen copper complex with <Emphasis Type="Italic">N</Emphasis>, <Emphasis Type="Italic">N</Emphasis>-bis-(1(2)H-tetrazol-5-yl) amine

A new high-nitrogen complex [Cu(Hbta)₂]·4H₂O (H₂bta = N,N-bis-(1(2)H-tetrazol-5-yl) amine) was synthesized and characterized by elemental analysis, single crystal X-ray diffraction and thermogravimetric analyses. X-ray structural analyses revealed that the crystal was monoclinic, space group P2(1)/c with lattice parameters a = 14.695(3) Å, b = 6.975(2) Å, c = 18.807(3) Å, β = 126.603(1)°, Z = 4, D _c = 1.888 g cm^?3, and F(000) = 892. The complex exhibits a 3D supermolecular structure which is built up from 1D zigzag chains. The enthalpy change of the reaction of formation for the complex was determined by an RD496–III microcalorimeter at 25 °C with the value of ?47.905 ± 0.021 kJ mol^?1. In addition, the thermodynamics of the reaction of formation of the complex was investigated and the fundamental parameters k, E, n, \( \Updelta S_{ \ne }^{{{\uptheta}}} \), \( \Updelta H_{ \ne }^{{{\uptheta}}} \), and \( \Updelta G_{ \ne }^{{{\uptheta}}} \) were obtained. The effects of the complex on the thermal decomposition behaviors of the main component of solid propellant (HMX and RDX) indicated that the complex possessed good performance for HMX and RDX.     

<Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> application as a prospective approach for biosynthesis of pyruvic acid from glycerol

With the problems related to chemical methods of pyruvic acid (PA) synthesis, a fast-growing interest has been observed in research aiming at reducing the production cost of PA by applying biotechnological methods. This study aimed to investigate the potential applicability of Yarrowia lipolytica Wratislavia 1.31 yeast strain for valorisation of pure and crude glycerol through the production of industrially desired PA. Conditions required for the effective PA biosynthesis, i.e., pH value, thiamine concentration, agitation, and substrate concentration, were examined in batch and fed-batch cultivation modes. The efficient production of PA occurred under the limitation of thiamine (1 µg L^?1) and was stimulated by moderate pH (4.5) and agitation (800 rev min^?1) of the culture. Under optimal conditions, Y. lipolytica Wratislavia 1.31 was able to produce 85.2 g L^?1 of PA with volumetric productivity of 0.90 g L^?1 h^?1. The yield of PA biosynthesis reached a high level of 1.03 g g^?1. Obtained results confirmed the aptitude of Y. lipolytica yeast to produce high amounts of PA from simple glycerol-containing media. Presented process was very promising and might be considered as an attractive alternative for currently used chemical methods of PA synthesis.     

Preconcentration and spectrophotometric determination of trace amount of formaldehyde using hollow fiber liquid-phase microextraction based on derivatization by Hantzsch reaction

Formaldehyde is known as a highly toxic compound to humans and identified as a carcinogenic substance. In this study, Hantzsch reaction was utilized for the derivatization of trace amounts of formaldehyde in aqueous samples with acetylacetone in the presence of ammonia to form an extractable colored product named 3,5-diacetyl 1,4-dihydrolutidine (DDL) and its further extraction using two-phase hollow fiber liquid-phase microextraction. The main experimental variables affecting the extraction performance were investigated and optimized. Under the optimum conditions (sample volume 12 mL; reaction temperature 70 °C; ammonium acetate buffer solution 4 mL 0.1 mol L^?1; acetylacetone 5 mL 0.15 mol L^?1; solvent octanol, salt concentration 20% (w/v) NaCl; pH of donor phase 7.0; stirring speed 400 rpm and extraction time 30 min), the linear dynamic range, limit of detection (LOD as 3S _b/m) and relative standard deviation (RSD %) of the proposed method were obtained as 5–250 μg L^?1 (r ² = 0.9979), 3.6 μg L^?1 and 2.5%, respectively. Finally, the applicability of the proposed method was examined, and very good results were obtained. The results confirmed the applicability of the proposed method as a versatile, low-cost and sensitive preconcentration method for determination of low concentrations of formaldehyde in aqueous solutions.     

Strain screening and sodium lactate effect on spiramycin production in <Emphasis Type="Italic">Streptomyces spiramyceticus</Emphasis>

Strain improvement and addition of sodium lactate to fermentation medium to enhance the productivity of spiramycin were performed. Of the sodium lactate tolerant mutants that were screened, one mutant, Streptomyces spiramyceticus 16-10-12, produced 23 % more spiramycin than the original strain, Streptomyces spiramyceticus 5-1. The effect of sodium lactate on spiramycin production with S. spiramyceticus 16-10-12 was studied. The titer was improved by 16.9 % with the addition of 15 g L^?1 sodium lactate in the fermentation medium at the beginning. The results from using the new process in a 15 L bioreactor showed that there were more precursors in fermentation broth with a sodium lactate tolerant mutant, and that these precursors were used more than with the original strain. After adding sodium lactate, the titer was increased by 23.4 %, because the flux to TCA circulation was increased, more precursors had been produced and the activities of Acyl-CoA synthetases, Acylphosphotransferases and Acylkinases in synthesis phase were also increased.     

Establishing a Mathematical Equations and Improving the Production of <Emphasis Type="SmallCaps">l</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Leucine by Uniform Design and Regression Analysis

l-tert-Leucine (l-Tle) and its derivatives are extensively used as crucial building blocks for chiral auxiliaries, pharmaceutically active ingredients, and ligands. Combining with formate dehydrogenase (FDH) for regenerating the expensive coenzyme NADH, leucine dehydrogenase (LeuDH) is continually used for synthesizing l-Tle from α-keto acid. A multilevel factorial experimental design was executed for research of this system. In this work, an efficient optimization method for improving the productivity of l-Tle was developed. And the mathematical model between different fermentation conditions and l-Tle yield was also determined in the form of the equation by using uniform design and regression analysis. The multivariate regression equation was conveniently implemented in water, with a space time yield of 505.9 g L^?1 day^?1 and an enantiomeric excess value of >99 %. These results demonstrated that this method might become an ideal protocol for industrial production of chiral compounds and unnatural amino acids such as chiral drug intermediates.     

Facile synthesis of 5A zeolite from attapulgite clay for adsorption of <Emphasis Type="Italic">n</Emphasis>-paraffins

5A zeolites were facilely synthesized from attapulgite clay and sodium aluminate precursors. The optimum synthesis condition for 4A zeolite (Na-form) were H₂O/attapulgite ratio of 40:1 volume/mass, NaOH/attapulgite mass ratio of 2.35:1, the crystallization time was 4 h at 80–85 °C. The 4A zeolite was converted to related 5A zeolite (Ca-form) through ionic exchanges using calcium chloride solution with the Si/Al mole ratio of 1.3. SEM images demonstrated that as-synthesized 5A zeolites are ordered cubic crystals, average crystals length dimension is 1–2 μm. And the zeolites product had a specific surface area of 482 m² g^?1 and total pore volume of 0.274 cm³ g^?1. The static adsorption experiments showed that the equilibrium adsorption capacities of n-decane and n-pentadecane on produced 5A zeolite were 0.253 and 0.510 g g^?1, respectively. And the adsorption equilibrium time of n-decane and n-pentadecane on 5A zeolite were 45 and 60 min, respectively. The experimental adsorption data of n-decane and n-pentadecane on three zeolites could be properly fitted by the Langmuir–Freundlich isotherm model.