Studies on RTD and continuous culture (SCP) in cylindrical and tapered reactors

The performance of a tapered reactor for the continuous cultivation of bakers' yeast (SCP) from cane molasses has been compared with that of a conventional cylindrical reactor. It is found that the tapered reactor has less non-idealities (bypass and deadspace).Using the experimentally evaluated bypass and deadspace values, a model for predicting conversions of substrate (cane molasses), based on the RTD model proposed by Cholette and Cloutier has been developed. The experimental substrate conversions are found to match the model satisfactorily.List of Symbols D h^–1 dilution rate - E() exit age distribution function - K _s kg/m³ Monod's saturation constant - -r _sa kg/(m³ · h) rate of substrate utilization - S kg/m³ substrate concentration expressed as dextrose equivalent (DE) - S _a kg/m³ substrate concentration in active zone - S ₀ kg/m³ initial substrate concentration - S/S ₀ dimensionless substrate concentration - v _a dm³/h volumetric flow through active zone - v _b dm³/h volumetric flow through bypass stream - u _l dm³/h substrate feed rate - v _g dm³/min air-flow rate - V dm³ total working volume of the reactor - V _a dm³ volume of active zone in reactor - V _d dm³ volume of dead zone in reactor - X kg/m³ biomass concentration Greek Letters fraction of bypass of feed, v _b /v _l - fraction of deadspace, V _d /V - dimensionless residence time - _m h^–1 maximum specific growth rate - h mean residence time, V/v _l      

The effect of micro- and macromixing on enzyme reaction in a real CSTR

The effect of micromixing and macromixing on enzyme reaction of Michaelis-Menten type in a real continuously stirred tank reactor (CSTR) is considered. The effect of bypassing of a fraction of feed stream, dead space, initial enzyme concentration and Michaelis-Menten constant on substrate conversion is evaluated. Bypass reduces the substrate conversion significantly compared with other parameters in the case of micro and macromixing. Micromixing predicts higher substrate conversions compared with macromixing. The effect of micro and macromixing on substrate conversion is negligible at low and high conversions.List of Symbols C kmol/m³ concentration of reactant - ¯C kmol/m³ average concentration of reactant - C_A kmol/m³ exit concentration of reactant A - C_Aa kmol/m³ exit concentration of reactant A from active zone - C_AO kmol/m³ initial concentration of reactant A - C_EO kmol/m³ initial enzyme concentration - C_O kmol/m³ initial concentration of reactant - E(t) 1/s exit age distribution function - k 1/s reaction rate constant - M kmol/m³ Michaelis-Menten constant - r kmol/(m³s) rate of reaction - –r_A kmol/(m³s) rate of reaction with respect to A - t s time - v m³/s volumetric feed rate - v_a m³/s volumetric feed rate entering the active zone - v_b m³/s volumetric feed rate entering the bypass stream - V m³ total volume of the vessel - V_a m³ active volume of the vessel - V_d m³ volume of dead space - X_A conversion of A Greek Letters fraction of feed stream bypassing the vessel (v_b/v) - fraction of the total volume as dead space (V_d/V) - (t) 1/s Dirac delta function, an ideal pulse occurring at time t = 0 - s life expectancy of a molecule - 1/s intensity function or escape probability function - s space time or mean residence time     

Purification of rabbit liver phosphofructokinase and its properties under simulatingin vivo conditions

Phosphofructokinase (EC 2.7.1.11) from rabbit liver was purified to homogeneity. Preincubation of enzyme results in nonlinearity of enzyme activity with enzyme concentration. Therefore K_0.5 of enzyme for fructose 6 phosphate in the absence or presence of fructose 2,6 bisphosphate or polyethylene glycol or in the presence of both was determined at physiological concentrations of its various effectors by taking the initial rate obtained by adding the enzyme last. They decrease the K_0.5 value from 4.1 mM to about 0.2mM. The K_0.5 of enzyme for fructose 2,6 bisphosphate was also determined under the above conditions. It is about 4.3ΜM. Transient kinetics of phosphofructokinase at varying concentrations of enzyme in the presence of fructose 2,6 bisphosphate or polyethylene glycol or in the presence of both were studied. It was found that although they decrease t_1/2 i.e. the time to reach half the maximal steady rate by about 5–8 fold, it was about constant at varying concentrations of the enzyme. These results indicate that fructose 2,6 bisphosphate and polyethylene glycol decrease K_0.5 of the enzyme for fructose 6 phosphate not by associating the enzyme to higher aggregates, but by a different mechanism.     

Synthesis and biological evaluation of 1-substituted-3-(6-methylpyridin-2-yl)-4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)pyrazoles as transforming growth factor-β type 1 receptor kinase inhibitors

A series of 1-substituted-3-(6-methylpyridin-2-yl)-4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)pyrazoles 14a-ae, 16a, 16b, and 21a-c has been prepared and evaluated for their ALK5 inhibitory activity in an enzyme assay and in a cell-based luciferase reporter assay. The 4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-N-(4-methoxyphenyl)-3-(6-methylpyridin-2-yl)-1H-pyrazole-1-carbothioamide (14n) inhibited ALK5 phosphorylation with IC(50) value of 0.57 nM and showed 94% inhibition at 100 nM in a luciferase reporter assay using HaCaT cells permanently transfected with p3TP-luc reporter construct.     

Linkage disequilibrium and population-structure analysis among Capsicum annuum L. cultivars for use in association mapping

Knowledge of population structure and linkage disequilibrium among the worldwide collections of peppers currently classified as hot, mild, sweet and ornamental types is indispensable for applying association mapping and genomic selection to improve pepper. The current study aimed to resolve the genetic diversity and relatedness of Capsicum annuum germplasm by use of simple sequence repeat (SSR) loci across all chromosomes in samples collected in 2011 and 2012. The physical distance covered by the entire set of SSRs used was 2,265.9 Mb from the 3.48-Gb hot-pepper genome size. The model-based program STRUCTURE was used to infer five clusters, which was further confirmed by classical molecular-genetic diversity analysis. Mean heterozygosity of various loci was estimated to be 0.15. Linkage disequilibrium (LD) was used to identify 17 LD blocks across various chromosomes with sizes from 0.154 Kb to 126.28 Mb. CAMS-142 of chromosome 1 was significantly associated with both capsaicin (CA) and dihydrocapsaicin (DCA) levels. Further, CAMS-142 was located in an LD block of 98.18 Mb. CAMS-142 amplified bands of 244, 268, 283 and 326 bp. Alleles 268 and 283 bp had positive effects on both CA and DCA levels, with an average R ² of 12.15 % (CA) and 12.3 % (DCA). Eight markers from seven different chromosomes were significantly associated with fruit weight, contributing an average effect of 15 %. CAMS-199, HpmsE082 and CAMS-190 are the three major quantitative trait loci located on chromosomes 8, 9, and 10, respectively, and were associated with fruit weight in samples from both years of the study. This research demonstrates the effectiveness of using genome-wide SSR-based markers to assess features of LD and genetic diversity within C. annuum.     

Regenerative Therapeutic Potential of Adipose Stromal Cells in Early Stage Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of blindness in working-age adults. Early stage DR involves inflammation, vascular leakage, apoptosis of vascular cells and neurodegeneration. In this study, we hypothesized that cells derived from the stromal fraction of adipose tissue (ASC) could therapeutically rescue early stage DR features. Streptozotocin (STZ) induced diabetic athymic nude rats received single intravitreal injection of human ASC into one eye and saline into the other eye. Two months post onset of diabetes, administration of ASC significantly improved “b” wave amplitude (as measured by electroretinogram) within 1–3 weeks of injection compared to saline treated diabetic eyes. Subsequently, retinal histopathological evaluation revealed a significant decrease in vascular leakage and apoptotic cells around the retinal vessels in the diabetic eyes that received ASC compared to the eyes that received saline injection. In addition, molecular analyses have shown down-regulation in inflammatory gene expression in diabetic retina that received ASC compared to eyes that received saline. Interestingly, ASC were found to be localized near retinal vessels at higher densities than seen in age matched non-diabetic retina that received ASC. In vitro, ASC displayed sustained proliferation and decreased apoptosis under hyperglycemic stress. In addition, ASC in co-culture with retinal endothelial cells enhance endothelial survival and collaborate to form vascular networks. Taken together, our findings suggest that ASC are able to rescue the neural retina from hyperglycemia-induced degeneration, resulting in importantly improved visual function. Our pre-clinical studies support the translational development of adipose stem cell-based therapy for DR to address both retinal capillary and neurodegeneration.     

Novel enzymatic technique for recovery of starch from whole cassava chips without mechanical pulverization

Summary Different commercial enzymes, used individually or in combination, released upto 96% starch from whole cassava chips with pectinase I and cellulase combination. The enzymic action on macerating chips and disintegrating root cells was dependent on size of chips, presence of peel, temperature, time, agitation and type as well as concentration of enzymes. Significantly higher starch recovery and elimination of cost-intensive mechanical pulverization indicate potential of the enzymic technique.     

Effect of α-p-chlorophenoxyisobutyrate on the metabolism of isoprenoid compounds in the rat

1. Feeding of alpha-p-chlorophenoxyisobutyrate (CPIB) to rats increased ubiquinone concentration in the liver but not in other tissues. The increase was progressive with the time of feeding and related to the concentration of CPIB in the diet. 2. Incorporation of [1-(14)C]acetate, but not of [2-(14)C]mevalonate, into sterols in the liver in vivo or by liver slices in vitro was decreased on feeding the rats with CPIB. However, incorporation of mevalonate into ubiquinone increased. 3. CPIB, when added in low concentrations to liver slices, had no effect on isoprene synthesis from acetate; higher concentrations, however, were inhibitory. 4. No activation of ubiquinone synthesis from mevalonate was observed when CPIB was added to the liver slices synthesizing ubiquinone. 5. The increase in ubiquinone in CPIB-fed animals appears to be due to increased synthesis in the initial stages and to decreased catabolism in the later stages. 6. An inverse relationship was found between the concentration of ubiquinone in the liver and the serum sterol concentration in CPIB-fed rats.     

A standard quantitative method to measure acid tolerance of probiotic cells

The aim of this work was to develop a standard quantitative method to measure the acid tolerance of probiotic cells when exposed to a simulated gastric fluid. Three model strains of different cell concentrations were exposed to a standard simulated gastric fluid of fixed volume. The fluid pH ranged from pH 1.5 to 2.5. In general, the death kinetics followed an exponential trend. The overall death constant, k _d, for all strains was found to be in a power relationship with the pH value and the initial cell concentration, and it can be expressed as

Inductively coupled plasma-optical emission spectrometry for on-line determination of multi trace elements in environmental samples after preconcentration by using Borassus flabellifer inflorescence loaded with 2-propylpiperidine-1-carbodithioate

A procedure was developed for the determination of Cu, Mn, Pb, Cd, Co, Cr, and Zn in water samples by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) after preconcentration on synthesized 2-propylpiperidine-1-carbodithioate supported by Borassus flabellifer Inflorescence (BFI). The sorbed element was subsequently eluted with 0.4 M HNO3, and the acid eluates were analyzed by ICP-OES. The influence of various parameters such as pH, flow rate of sample, eluent concentration, volume of the sample, and volume of eluent were investigated. Under the optimal conditions, Cu, Mn, Pb, Cd, Co, Cr, and Zn in aqueous samples were concentrated ca. 100-fold. Recoveries were obtained by the proposed method in the range of 97.8-99.9%. This method was also applied for the analysis of spiked, natural waters and soil samples. The results provide strong evidence to support the hypothesis of an adsorption mechanism.