Kinetics of Avermectin B1b Production by Streptomyces avermitilis 41445 UV 45(m)3 in Shake Flask Culture.

BACKGROUND: Use of avermectin B1b as anthelmintic and insecticidal agent has increased to protect soil and for enhanced crop production. Enhanced production of avermectin B1b was obtained from mutant strain of Streptomyces avermitilis 41445. OBJECTIVES: Modeling of mutant strain S. avermitilis 41445 UV 45(m) 3 growth and avermectin B1b production is therefore required for optimization during fermentation process. Kinetics of intracellular avermectin B1b production was studies in shake flask culture during submerged fermentation. MATERIALS AND METHODS: Mathematical models based upon Logistic and Piret Equations have been used to investigate the kinetics of avermectin B1b production and substrate utilization from S. avermitilis 41445 UV 45(m)3. Effect of carbon sources (glucose, maltose, lactose, potato starch, soluble corn starch, and wheat starch), pH (6.0, 6.5, 7.0, and 7.5), agitation speed (150, 200, and 250 rpm) on microbial growth and product formation were evaluated. RESULTS: Maximum avermectin B1b production (420.02mg.L-1 and cell biomass (31.74 g.L-1) were obtained in media having potato starch as carbon substrate at adjusted medium pH 7.5 and 250 rpm agitation speed. Maximum specific growth rate(µmax), growth associated avermectin B1b production coefficient (α) and non-growth associated avermectin B1b production coefficient (ß) obtained were 0.16h-1, 0.0 mg.g-1 and 3.5 mg.g-1.h-1 respectively. CONCLUSION: From above results we can conclude that avermectin B1b production is non-growth associated process.

Design, synthesis, characterization and computational docking studies of novel sulfonamide derivatives.

This study reports three novel sulfonamide derivatives 4-Chloro-N-[(4-methylphenyl) sulphonyl]-N-propyl benzamide (1A), N-(2-hydroxyphenyl)-4-methyl benzene sulfonamide (1B) and 4-methyl-N-(2-nitrophenyl) benzene sulfonamide (1C). The compounds were synthesised from starting material 4-methylbenzenesulfonyl chloride and their structure was studied through 1H-NMR and 13C-NMR spectra. Computational docking was performed to estimate their binding energy against bacterial p-amino benzoic acid (PABA) receptor, the dihydropteroate synthase (DHPS). The derivatives were tested in vitro for their antimicrobial activity against Gram+ and Gram- bacteria including E. coli, B. subtilis, B. licheniformis and B. linen. 1A was found active only against B. linen; 1B was effective against E. coli, B. subtilis and B. linen whereas 1C showed activity against E. coli, B. licheniformis and B. linen. 1C showed maximum activity with minimum inhibitory concentration (MIC) of 50, 100 and 150 µg/mL against E. coli, B. licheniformis and B. linen respectively. 1C exhibited maximum affinity to DHPS with binding free energy of -8.1 kcal/mol. It enriched in the top 0.5 % of a library of 7663 compounds, ranked in order of their binding affinity against DHPS. 1C was followed by 1B which showed a moderate to low level MIC of 100, 250 and 150 µg/mL against E. coli, B. subtilis and B. linen respectively, whereas 1A showed a moderate level MIC of 100 µg/mL but only against B. linen. These derivatives may thus serve as potential anti-bacterial alternatives against resistant pathogens.

Isolation, Characterization and Selection of Avermectin-Producing Streptomyces avermitilis Strains From Soil Samples.

BACKGROUND: Streptomyces avermitilis, belonging to Actinomycetes, is specialized for production of avermectin, used as an anthelmintic and insecticidal agent. It is mostly found in soil and its isolation is very crucial for medically important avermectin production. OBJECTIVES: In the present study, 10 bacterial isolates lacking antimicrobial activities were isolated from the soil samples collected from different areas of Lahore, Pakistan. MATERIALS AND METHODS: Three distinctive localities of Lahore were opted for soil assortment to isolate S. avermitilis. About 50 isolates of Streptomyces species were attained through selective prescreening procedures. All of these isolates were studied for production of the secondary metabolite, avermectin. Different test like soluble pigment color and melanin formation were used for identification. Biochemical characterizations of those isolates closely resembling the control in morphological characteristics, soluble pigment color and melanin formation tests were performed. RESULTS: The 10 selected isolates were identified as the avermectin-producing strain by fermentation and characterized on ISP2 medium for aerial and reverse side mycelia color, soluble pigment color and melanin formation, in comparison with S. avermitilis DSM 41445. The best avermectin-producing isolate S1-C (10.15 mg/L) showed similar result as S. avermitilis DSM 41445, when subjected for culture characteristics analysis in different media along with biochemical characterization. CONCLUSIONS: From the results, it was concluded that agricultural lands around Pakistan Council of Scientific and Industrial Research (PCSIR) Campus Lahore were rich sources of industrially important Streptomyces, especially S. avermitilis.

Production and Screening of High Yield Avermectin B1b Mutant of Streptomyces avermitilis 41445 Through Mutagenesis.

BACKGROUND: Secondary metabolite production from wild strains is very low for economical purpose therefore certain strain improvement strategies are required to achieve hundred times greater yield of metabolites. Most important strain improvement techniques include physical and chemical mutagenesis. Broad spectrum mutagenesis through UV irradiation is the most important and convenient physical method. OBJECTIVES: The present study was conducted for enhanced production of avermectin B1b from Streptomyces avermitilis 41445 by mutagenesis using ultraviolet (UV) radiation, ethidium bromide (EB), and ethyl methanesulfonate (EMS) as mutagens. MATERIALS AND METHODS: S. avermitilis DSM 41445 maintained on yeast extract malt extract glucose medium (YMG) was used as inoculum for SM2 fermentation medium. Spores of S. avermitilis DSM 41445 were exposed to UV radiation for physical broad spectrum mutagenesis and to EMS and EB for chemical mutagenesis. For each mutagen, the lethality rate and mutation rate were calculated along with positive mutation rate. RESULTS: Avermectin B1b-hyper-producing mutant, produced using these three different methods, was selected according to the HPLC results. The mutant obtained after 45 minutes of UV radiation to the spores of S. avermitilis 41445, was found to be the best mutant for the enhanced production of avermectin B1b component (254.14 mg/L). Other avermectin B1b-hyper-producing mutants, were obtained from EMS (1 µL/mL) and EB (30 µL/mL) treatments, and yielded 202.63 mg/L and 199.30 mg/L of B1b, respectively. CONCLUSIONS: The hereditary stability analysis of the UV mentioning 45 minutes revealed the UV exposure time for mutants and 3 represented the colony taken from the plate irradiated for 45 minutes mutant showed that the production of avermectin B1b remained constant and no reverse mutation occurred after 15 generations.

Optimization of sulfide/sulfite pretreatment of lignocellulosic biomass for lactic acid production.

Potential of sodium sulfide and sodium sulfite, in the presence of sodium hydroxide was investigated to pretreat the corncob (CC), bagasse (BG), water hyacinth and rice husk (RH) for maximum digestibility. Response Surface Methodology was employed for the optimization of pretreatment factors such as temperature, time and concentration of Na2S and Na2SO3, which had high coefficient of determination (R²) along with low probability value (P), indicating the reliable predictability of the model. At optimized conditions, Na2S and Na2SO3 remove up to 97% lignin, from WH and RH, along with removal of hemicellulose (up to 93%) during pretreatment providing maximum cellulose, while in BG and CC; 75.0% and 90.0% reduction in lignin and hemicellulose was observed. Saccharification efficiency of RH, WH, BG and CC after treatment with 1.0% Na2S at 130°C for 2.3-3.0 h was 79.40, 85.93, 87.70, and 88.43%, respectively. WH treated with Na2SO3 showed higher hydrolysis yield (86.34%) as compared to Na2S while other biomass substrates showed 2.0-3.0% less yield with Na2SO3. Resulting sugars were evaluated as substrate for lactic acid production, yielding 26.48, 25.36, 31.73, and 30.31 gL⁻¹ of lactic acid with 76.0, 76.0, 86.0, and 83.0% conversion yield from CC, BG, WH, and RH hydrolyzate, respectively.

Enzymatic saccharification and lactic acid production from banana pseudo-stem through optimized pretreatment at lowest catalyst concentration.

This work estimates the potential of banana pseudo-stem with high cellulosic content 42.2-63 %, for the production of fermentable sugars for lactic acid production through statistically optimized pretreatment method. To evaluate the catalyzed pretreatment efficiency of banana pseudo stem based on the enzymatic digestibility, Response Surface Methodology (RSM) was employed for the optimization of pretreatment temperature and time using lowest concentrations of H2SO4, NaOH, NaOH catalyzed Na2S and Na2SO3 that seemed to be significant variables with P<0.05. High F and R (2) values and low p-value for hydrolysis yield indicated the model predictability. The optimized condition for NaOH was determined to be conc. 1 %, temperature 130 (o)C for 2.6 hr; Na2S; conc. 1 %, temperature 130 (o)C for 2.29 hr; Na2SO3; conc. 1 %, temperature 130 (o)C for 2.41 hr and H2SO4; conc. 1 %, temperature 129.45 (o)C for 2.18 hr, produced 84.91 %, 85.23 %, 81.2 % and 76.02 % hydrolysis yield, respectively. Sulphuric acid provided 33+1 gL(-1) reducing sugars in pretreatment step along with 38+0.5 gL(-1) during enzymatic hydrolysis. Separate hydrolysis and fermentation of resulting sugars showed that the conversion of glucans into lactic acid reached 92 % of the theoretical yield of glucose.

N-[4-(Propyl-sulfamo-yl)phen-yl]acetamide.

In the title compound, C(11)H(16)N(2)O(3)S, the S atom has a distorted tetra-hedral geometry [maximum deviation: O-S-O = 119.48 (15)°]. The dihedral angles between the benzene ring and its propyl-sulfonamide and methyl-amide substituents are 71.8 (2) and 5.8 (1)°, respectively. In the crystal, mol-ecules are linked by N(m)-H⋯O(s) (m = methyl-amide and s = sulfonamide) hydrogen bonds, forming C(8) chains along the a axis. The two mol-ecule chains are connected by N-H⋯O hydrogen bonds, generating R(3) (2)(18) rings. The crystal packing is further stabilized by weak inter-molecular C-H⋯O hydrogen bonds.

N-Ethyl-N-(4-methyl-phen-yl)benzene-sulfonamide.

The title compound, C(15)H(17)NO(2)S, is twisted at the S-N bond with a C-S-N-C torsion angle of 73.90 (14)°. The dihedral angle between the aromatic rings is 36.76 (11)°.

N-{4-[(3-Methyl-phen-yl)sulfamo-yl]phen-yl}acetamide.

In the title compound, C(15)H(16)N(2)O(3)S, the central C-S(=O)(2)N(H)-C unit is twisted, with a C-S-N-C torsion angle of -56.4 (2)°. The benzene rings form a dihedral angle of 49.65 (15)° with each other. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, generating a three-dimensional network.

Preparation and characterization of chloramphenicol niosomes and comparison with chloramphenicol eye drops (0.5%w/v) in experimental conjunctivitis in albino rabbits.

Niosomes has gained tremendous popularity as ultimate drug carrier. Lot of research work is being carried out on preparation of niosomes for ophthalmic use having no significant effect on vision and its sustained release pattern. Chloramphenicol niosomes were prepared using two different ratios of cholesterol, drug and surfactant, termed as EIN-1, EIN-2 by ether injection method and their entrapment efficiency, particle size. The in vitro drug release pattern was observed for ten hours. The EIN-2 showed 90% entrapment and released 81% of entrapped drug after 10 hours. Zeta potential & viscosity were determined and in-vivo comparison was made with Chloramphenicol eye drops where it exhibited Cmax of 15 µ g/ml. Stability studies were done to determine shelf life. MIC of selected strain of S. aureus was also determined. EIN 2 niosomal suspension was compared with Chloramphenicol eye drops in experimental conjunctivitis in albino rabbits. In-vitro studies are encouraging as niosomes released about 75% of total entrapped drug by EIN-1 and 81% of total entrapped drug by EIN 2. In vivo study shows that niosomes released the drug in eye in acceptable range and showed a sustained release pattern without affecting the vision. Niosomes were found ultimate ophthalmic drug carriers capable to release drug in sustained and determined pattern.

N-Ethyl-4-methyl-N-(3-methyl-phen-yl)benzene-sulfonamide.

The title compound, C(16)H(19)NO(2)S, crystallizes with two crystallographically independent mol-ecules in the asymmetric unit in which the dihedral angles between the planes defined by the aromatic rings are 35.3 (2) and 42.5 (2)°. In the crystal, inter-molecular C-H⋯O hydrogen bonds stabilize the packing.

N-Benzyl-4-methyl-N-(4-methyl-phen-yl)benzene-sulfonamide.

In the title mol-ecule, C(21)H(21)NO(2)S, the phenyl ring makes the dihedral angles of 74.13 (11) and 80.16 (11)° with the two benzene rings, which are inclined at an angle of 43.73 (10)° with respect to each other. In the crystal, mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonds along the [010] direction. In addition, a weak C-H⋯π (arene) inter-action is observed.

N-{4-[(2-Meth-oxy-phen-yl)sulfamo-yl]phen-yl}acetamide.

In the title compound, C(15)H(16)N(2)O(4)S, the S atom has a distorted tetra-hedral geometry [maximum deviation: O-S-O = 118.25 (7)°]. The two aromatic rings make a dihedral angle of 62.67 (10)° with each other. An intra-molecular N-H⋯O hydrogen bond forms an S(6) ring motif. In the crystal, mol-ecules form centrosymmetric dimers via pairwise N-H⋯O inter-actions, forming an R(2) (2)(8) ring motif, and these dimers are connected by N-H⋯O hydrogen bonds, generating a three-dimensional network. Furthermore, a weak C-H⋯π inter-action helps to reinforce the crystal structure. The O atom in the acetamide group is disordered over two positions with major and minor occupancies of 0.52 (5) and 0.48 (5), respectively.