Optimization of fermentation conditions for production of glycopeptide antibiotic vancomycin by Amycolatopsis orientalis

Glycopeptides produced by Streptomyces species are the drugs used against β-lactam drug-resistant staphylococcal infections, and vancomycin is important among them. Increased prevalence of resistant strains increased the usage of vancomycin worldwide and also promoted attempts for indigenous production. The optimum process conditions pH, temperature, inoculum size, agitation, and aeration for vancomycin production by Amycolatopsis orientalis were evaluated, statistically analyzed, and the response surface curves were constructed. The optimum process conditions were a pH of 7.6, a temperature of 29°C, an inoculum size of 4.5%, an agitation of 255 rpm, and an aeration of less than 1:10 medium-to-air ratio.     

Resistance-in-series analysis in cross-flow ultrafiltration of fermentation broths of Bacillus subtilis culture

Quantitative analysis of various resistances that lead to flux decline during cross-flow ultrafiltration (UF) of the fermentation broth of Bacillus subtilis ATCC (American Type Culture Collection) 21332 culture was studied. Polyethersulfone membrane with a molecular weight cut-off (MWCO) of 100 kDa was used. Prior to cross-flow UF, the broth was treated by acid precipitation (pH 4.0) and centrifugation, and the precipitate was re-dissolved in NaOH solution. Experiments were performed at a feed pH of 7.0, a feed surfactin concentration of 1.48 g L⁻¹, and a cross-flow velocity of 0.32 m s⁻¹ but at different transmembrane pressures (ΔP, 20–100 kPa). The resistance-in-series model was used to analyze the flux behavior, which involves the resistances of membrane itself and cake as well as those due to adsorption and solute concentration polarization. It was shown that the resistance due to solute concentration polarization and of membrane dominated under the conditions examined. The resistances due to cake formation and solute adsorption were comparable, and their sum contributed below 20% of the overall resistance.     

Rheological behavior of fumed silica filled polyethylene oxide

Influence of molecular weight of polymer matrix on nanocomposites rheology is not yet well understood. Herein dynamic rheological responses of fumed silica (FS)/polyethylene oxide (PEO) nanocomposites are investigated as a function of viscosity‐averaged molecular weight (M_η) of PEO, volume fraction (?) and surface characteristics (hydrophilic or hydrophobic) of FS. In the nanocomposites, FS does not influence the glass transition and crystallinity of PEO in the mobile PEO phase while the interfacial interactions tend to immobilize a small fraction of PEO chains that could not undergo glass transition. In spite of the common observation that the reinforcement decreases with increasing M_η of PEO and improving hydrophobicity of FS, linear rheological responses are well reproduced by the two‐phase model, revealing the crucial contribution of the non‐Newtonian matrix undergoing microscopic strain amplified by the filler. Furthermore, nonlinear rheological responses of the nanocomposites are collapsed into master curves plotted against local strain of the matrix. Analyzing the nonlinear rheology by Fourier transform and stress waveform methods reveal the dominating contribution of the matrix and the role of strain amplification played by the filler. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 397–405     

A rapid HPLC determination of narasin in fermentation broth

Summary A rapid HPLC assay with post-column derivatization has been developed for the determination of narasin in fermentation broth. The reaction of narasin with substituted benzaldehydes was investigated under first order conditions and the rate constants were determined for a variety of substituted benzaldehydes. Vanillin reacted most rapidly to produce a red color. The reaction conditions were optimized to acheive a maximum response with a minimum analysis time.     

Extraction of surfactin from fermentation broth with n-hexane in microporous PVDF hollow fibers: Significance of membrane adsorption

In order to avoid foaming behavior and the formation of stable emulsions in traditional extraction, non-dispersive extraction of surfactin from the fermentation broth of Bacillus subtilis ATCC 21332 culture with n-hexane was studied in microporous polyvinylidene fluoride (PVDF, pore size 0.2 μm) hollow fiber module. In this work, the broth was pretreated by acid precipitation and the precipitate was then dissolved in NaOH solution, and the treated broth was passed through the lumen side of the module and n-hexane was flowed across the shell side. Experiments were performed at a fixed pH of 8.0 and a flow rate of both phases of 2.5 mL min⁻¹ but at different surfactin concentrations (300–3000 mg L⁻¹). Under the conditions studied, it was shown that surfactin was adsorbed onto the surface of the fibers, instead of being extracted by n-hexane and transported through the pores of the fibers into bulk n-hexane phase. The adsorption capacity was determined and the adsorption dynamics was analyzed. The purity of surfactin desorbed from the fibers with ethanol was found to be higher than that obtained after solvent extraction with n-hexane.     

HPLC‐ELSD determination of kanamycin B in the presence of kanamycin A in fermentation broth

A novel method for the direct determination of kanamycin B in the presence of kanamycin A in fermentation broth using high performance liquid chromatography with evaporative light scattering detector (HPLC‐ELSD) was developed. An Agilent Technologies C₁₈ column was utilized, evaporation temperature of 40°C and nitrogen pressure of 3.5 bar, the optimized mobile phase was water–acetonitrile (65:35, v/v), containing 11.6 mm heptafluorobutyric acid (isocratic elution with flow rate of 0.5 mL/min) with the gain 11. Kanamycin B was eluted at 5.6 min with an asymmetry factor of 1.827. The method showed good linearity over the concentration range of 0.05 to 0.80 mg/mL for the kanamycin B (r² = 0.9987). The intra‐day and inter‐day coefficients of variation obtained from kanamycin B were less than 4.3%. Mean recovery of kanamycin B from spiked fermentation broth was 95%. The developed method was applied to the determination of kanamycin B without any interference from other constituents in the fermentation broth. This method offers simple, rapid and quantitative detection of kanamycin B. Copyright © 2014 John Wiley & Sons, Ltd.     

Rheological Analysis of Biopolymer Produced by Aureobasidium Pullulans in Different Sources of Nitrogen

Summary: In this study, the rheological behaviors of media fermented by two Aureobasidium pullulans strains (IOC 3467 and IOC 3011) were evaluated in different nutritional conditions. The media consisted of crystal sugar (sucrose), as the main carbon source, and different nitrogen sources (ammonium sulfate, sodium nitrate, ammonium nitrate, urea or residual brewery yeast - RBY). Viscosity measurements were performed on cell-free supernatants, from 48-hour fermentation assays, at 25 ^°C. Shear rates ranged between 0.1000 and 500 s⁻¹. All samples showed pseudoplastic behavior. Nevertheless, the viscosimetric profile of each one varied according to the nitrogen source, its concentration and the strain used. The maximum viscosity of 0.06 Pa.s. was achieved at 15.6 s⁻¹ for IOC 3011 strain grown on RBY as nitrogen source.     

高效液相色谱法同时测定发酵液中赤藓糖醇和L-赤藓酮糖的含量

建立了采用高效液相色谱(HPLC)同时测定发酵液中底物赤藓糖醇和产物L-赤藓酮糖含量的方法。采用Lichrospher 5-NH2色谱柱(250 mm×4.6 mm),柱温30 ℃,以乙腈-水(体积比为9:1)为流动相,流速1.0 mL/min。用示差折光检测器检测赤藓糖醇,检测器温度为35 ℃。用紫外检测器在室温下检测L-赤藓酮糖,检测波长为277 nm。所得赤藓糖醇的线性范围为1.00～100.00 g/L,相关系数为0.9985,检出限为0.10 g/L,定量限为0.45 g/L;所得L-赤藓酮糖的线性范围为1.00～100.00 g/L,相关系数为0.9958,检出限为0.50 g/L,定量限为0.87 g/L;赤藓糖醇的日内和日间相对标准偏差(RSD)分别小于3.28%和5.30%, L-赤藓酮糖的日内和日间RSD分别小于2.16%和2.25%;回收率均大于99%。取不同时间的发酵液样品分别用上述方法测定,结果表明所建立的HPLC法不受发酵液中其他组分的影响,可同时测定底物赤藓糖醇和产物L-赤藓酮糖的含量。     

Model-based design of a pilot-scale simulated moving bed for purification of citric acid from fermentation broth

One of the conventional processes used for the recovery of citric acid from its fermentation broth is environmentally harmful and cost intensive. In this work an innovative benign process, which comprises simulated moving bed (SMB) technology and use of a tailor-made tertiary poly(4-vinylpyridine) (PVP) resin as a stationary phase is proposed. This paper focuses on a model-based design of the operation conditions for an existing pilot-scale SMB plant. The SMB unit is modeled on the basis of experimentally determined hydrodynamics, thermodynamics and mass transfer characteristics in a single chromatographic column. Three mathematical models are applied and validated for the prediction of the experimentally attained breakthrough and elution profiles of citric acid and the main impurity component (glucose). The transport dispersive model was selected for the SMB simulation and design studies, since it gives a satisfactory prediction of the elution profiles within acceptable computational time. The equivalent true moving bed (TMB) and SMB models give a good prediction of the experimentally attained SMB separation performances, obtained with a real clarified and concentrated fermentation broth as a feed mixture. The SMB separation requirements are set to at least 99.8% citric acid purity and 90% citric acid recovery in the extract stream. The complete regeneration in sections 1 and 4 is unnecessary. Therefore the net flow rates in all four SMB sections have been considered in the unit design. The influences of the operating conditions (the flow rate in each section, switching time and unit configuration) on the SMB performances were investigated systematically. The resulting SMB design provides 99.8% citric acid purity and 97.2% citric acid recovery in the extract. In addition the citric acid concentration in the extract is a half of its concentration in the pretreated fermentation broth (feed).     

Rheological behavior of polypropylene/octavinyl polyhedral oligomeric silsesquioxane composites

The reactive blending composites of isotactic polypropylene (PP)/octavinyl polyhedral oligomeric silsesquioxane (POSS) were prepared in the presence of dicumyl peroxide. Comparison of the rheological behavior of physical and reactive blending composites was made by oscillatory rheological measurements. It was found that the viscosity of physical blending composites drops at lower POSS content (0.5–1 wt %) and thereafter increases with increasing POSS content; that of reactive blending composites increases with increasing POSS content and displays a solid‐like rheological behavior at low frequency region when POSS content is higher than 1 wt %. The deviation of reactive blending composites from the scaling log G′–log G″ of linear polymer in Han plot, upturning at high viscosity in Cole–Cole plot, and from van Gurp–Palmen plot are related to the gelation behavior reactively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 526–533, 2008     

纤维素酶在食品发酵工业中的应用及其前景

本文论述了纤维素与纤维素酶的研究进展。着重阐述了纤维素酶在食品与发酵工业中的应用及其木质纤维类废物利用等最新动态、同时阐明了纤维素与纤维素酶在食品及发酵工业应用中存在的问题。     

Rheological behavior of moderately concentrated silica suspensions in the presence of adsorbed poly(ethylene oxide)

Adsorption and flocculation properties have been investigated for a well-characterized aqueous system of precipitated nanometric silicabeads in the presence of a high molecular-weight poly(ethylene oxide). Particular attention was given to the evolution of these properties with increasing concentration. In addition, the corresponding consequences on the rheological behavior in the homogeneous domains of the phase diagram of the systems were studied. Important rheological effects can actually be obtained with such systems, even at moderate values of the volume fraction of the dispersed phase (5·10^–35·10^–2).According to the adsorption level, the number of particles per macromolecular chain, and the free polymer equilibrium concentration, quite different phenomena were observed such as rheopectic shear-induced gelation, Newtonian flow or thixotropic shear-thinning.     

Rheological behavior of PET/HDPE in situ microfibrillar blends: Influence of microfibrils' flexibility

Poly(ethylene terephthalate) (PET)/high‐density polyethylene (HDPE) in situ microfibrillar reinforced blends were prepared via a slit die extrusion‐hot stretch‐quenching process. The in situ PET microfibrils contain various contents of a segmented thermoplastic elastomer, Hytrel 5526 (HT), hence having different flexibility as demonstrated by dynamic mechanical analysis. It is interesting that the simple mixing leads to nanoscale particles of the HT phase in PET phase, and the size of the HT particles is almost independent of the HT concentration, as observed from the scanning electron microscope micrographs which show that the microfibrils with different HT concentrations have almost the same diameter and smooth surfaces. The static rheological results by an advanced capillary rheometer show that the entrance pressure drop and the viscosity of the microfibrillar blends both reduced with increasing the microfibrils' flexibility. Furthermore, the data obtained by the temperature scan of the PET/HT/HDPE microfibrillar blends through a dynamic rheometer indicates that the more flexible microfibril leads to lower melt elasticity and slightly decreases the viscosities of blends, presenting a consistent conclusion about influences of the microfibrils' flexibility on the rheological behavior from the static rheometer measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1205–1216, 2007     

Determination of erythromycins in fermentation broth using liquid phase extraction with back extraction combined with high performance liquid chromatography

Liquid phase extraction with back extraction (LPE-BE) combined with high performance liquid chromatography-diode array detection (HPLC-DAD) was applied for the extraction and determination of erythromycin A, B and C in fermentation broths. According to this procedure, the fermentation broth with the adjustment pH at a fixed value of 10 was first mixed with organic solvent (V_broth/V_org = 1.0). After shaking, the mixture was separated into two phases by microfuging at 13,000 rpm for 15 min. Then back extraction was performed into the acidic aqueous phase with pH 5.0 (V_org/V_aq = 1.0). After centrifugation at 3000, the two phases were separated and 50 μL of the acidic aqueous phase was injected into the HPLC. The effects of different variables such as the nature of extraction solvent and the pH of samples and buffer were investigated. At the most appropriate conditions, dynamic linear ranges of 0.5–8, 0.1–0.9 and 0.1–0.9 mg mL⁻¹ and limits of detection of 0.03, 0.003 and 0.002 mg mL⁻¹ were obtained for erythromycin A, B and C, respectively. Relative standard deviations (RSDs) of the proposed method were less than 9.5%. The mean recoveries were 99.5%. The proposed method is simple and sensitive with highly clean-up effect and it can be used for monitoring the progress of erythromycin fermentation.     

Optimization of l‐arginine purification from Corynebacterium crenatum fermentation broth

l ‐Arginine has many special physiological and biochemical functions, with wide applications in the food and pharmaceutical industry. Few studies on the purification of l ‐arginine from fermentation broth have been conducted; however, none of them were systematic enough for industrial scale‐up. Therefore, it is necessary to develop a highly efficient and systematic process for the purification of l ‐arginine from fermentation broth. In this study, we screened out a cation exchange resin, D155, having high exchange capacity, high selectivity, and easy elution capacity, and analyzed its adsorption isotherm, thermodynamics, and kinetics using different models. Further, the process parameters of fixed‐bed ion exchange adsorption and elution were optimized, and the penetration curve during the operation was modeled. Based on the fixed‐bed ion‐exchange parameters, a 30‐column continuous ion‐exchange system was designed, and the flow velocity in each zone was optimized. Finally, to obtain a high purity of l ‐arginine, the purification tests were conducted using anion exchange resin 711, and an l ‐arginine yield of 99.1% and purity of 98.5% was obtained. This effective and economical method also provides a promising strategy for separation of other amino acids from the fermentation broth, which is of great significance to the l ‐arginine fermentation industry.     

Determination of monensins A and B in the fermentation broth ofStreptomyces cinnamonensis by high performance liquid chromatography

Summary High performance liquid chromatography on an octadecyl silica column has been used to determine both the monensin A: monensin B ratio and by the method of standard addition, the concentration of both in the fermentation broth ofStreptomyces cinnamonensis. Refractive index detection was preferred to ultraviolet owing to the presence of UV-absorbing components which could not be completely separated from the substances of interest. A linear relationship was obtained from the calibration data. The coefficients of variation for the estimation both of the ratio and the concentrations of the compounds were better then 5%. The estimated limit of detection for both substances was about 1 g/ml. The results obtained from the determination of the ratios of monensins were compared with those obtained by chemical ionization mass spectrometry. Chromatographic separation of monensins on the silica gel column is also described.     

Importance of growth form on production of hybrid antibiotic byStreptomyces lividans TK21 by fed-batch and continuous fermentation

A fermentation strategy, based on the controlled feeding of growthlimiting nutrients in order to maintain metabolic activity for extended periods, has been examined in the case of the production of a hybrid antibiotic by a transformed strain ofStreptomyces lividans TK21. The fed-batch operation did not improve the results obtained with batch operation. Continuous cultures on defined medium showed stable levels of biomass concentration, but antibiotic production ceased when continuous operation was started. The results obtained indicate the critical influence that morphology of the cell aggregates has on metabolic activity. The antibiotic is produced only in culture conditions providing growth in compact mycelial pellets.     

Physico-chemical characteristics of vernamycin-A antibiotic biosynthesis by streptomyces SP-AZ-SH-29

Seventy-five actinomycete isolates were isolated from different soil samples collected from different localities in Egypt. One of the actinomycete culture AZ-SH-29 from three cultures was found to produce a wide spectrum antimicrobial agent. The actinomycete isolate AZ-SH-29 matches with Streptomyces ramulosus in the morphological, physiological, and biochemical characters. Thus, it was given the suggested name Streptomyces ramulosus-AZ-SH-29. The parameters controlling the biosynthetic process of the antimicrobial agent formation including; different pH values, different temperatures, different incubation period, and different carbon and nitrogen sources, were fully investigated. The active metabolite was extracted using ethyl acetate (1:1, v/v) at pH 7.0. The separation of the active ingredient and its purification were performed using column chromatography (CC) technique. The physico-chemical characteristics of the purified antimicrobial agent have been investigated. This analysis indicates a suggested imperical formula of C₂₀H₂₅N₂O₅. The minimum inhibition concentrations “MICs” of the purified antibiotic and antiviral test were also determined. The purified antimicrobial agent was suggestive of being belonging to Depsipeptide (Mikamycin) group (Vernamycin-A antibiotic) produced by Streptomyces ramulosus, AZ-SH-29.     

分光光度法测定微生物发酵液中D-核糖浓度及其机理

研究了发酵液中D-核糖的分光光度测定方法。根据分光光度测定D-核糖的原理，研究了发酵液中D-核糖的测定影响因素和规律。得出最佳的测定波长为670nm、加热时间为25min、氢离子浓度为8mol/L、D-核糖浓度在10-30mg/L范围内吸光度A与D-核糖浓度有线性关系，发酵液中的非葡萄糖成分的影响可忽略。葡萄糖对D-核糖的测定影响显著，通过实验得出其变化规律。建立了分光光度法测定微生物发酵液中D-核糖浓度测定的有效方法。