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Chetan Joshi,Rekha Satishchandra Singhal 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.1
The operational optimization of zeaxanthin production by Paracoccus zeaxanthinifaciens ATCC 21588 in a bubble column reactor was performed by coupling genetic algorithm (GA) to an artificial neural network (ANN) model developed using experimental one-variable-at-a-time (OVAT) results. The effects of varying air flow rate (2- 5 vvm) and inoculum size (4 and 8%) for different incubation time (30-80 h) were evaluated. Volumetric power input (P/VL) and energy input (E) to the bubble column were then correlated with the ANN-GA optimized conditions. A maximum zeaxanthin production of 13.76±0.14mg/L was observed at 4 vvm using an inoculum size of 4% (v/v) after 60h of incubation in OVAT experiments with corresponding P/VL value of 231.57 W/m3 reflecting an energy consumption of 50.02 kJ during the fermentation period. The ANN based GA optimization predicted a maximum zeaxanthin production of 14.79mg/L at 3.507 vvm, 4% inoculum size and 55.83 h against the experimental production of 15.09±0.51mg/L corresponding to a P/VL value of 202.03 W/m3 reflecting to a significantly reduced energy input (40.01 kJ). The proposed OVAT based ANN-GA optimization approach can be used to simulate similar studies involving microbial fermentation in bioreactors.
Iyer Padma,Rekha Singhal 한국생물공학회 2010 Biotechnology and Bioprocess Engineering Vol.15 No.6
A culture isolated from garden soil was found to be a promising L-glutaminase producer. Biochemical identification tests and 16S rRNA sequencing identified this isolate to be Klebsiella oxytoca. Subsequently, media optimization using one-factor-at-a-time approach and response surface methodology was undertaken. A face centered central composite design was employed to investigate the interactive effects of four variables, viz. concentrations of maltose, yeast extract, beef extract, and ammonium acetate on glutaminase production. Almost all factors had significant interactive effects on glutaminase production. A medium containing (g/L): maltose, 23.31; yeast extract, 20.0; beef extract, 20.01; ammonium acetate, 10.0; mannitol, 10.0;KH2PO4, 0.4; Na2SO4, 0.4; and MgCl2, 0.4 was optimum for glutaminase production. The applied methodology was validated using this optimized media and enzyme activity of 458.91 ± 9.49 U/L and specific activity of 0.441 ± 0.04U/mg protein after 42 h of incubation at 33oC were obtained.
Metabolic Precursors and Cofactors Stimulate Astaxanthin Production in Paracoccus MBIC 01143
Jyoti A. Chougle,Rekha S. Singhal 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.6
This work investigates bacterial production of astaxanthin as an alternative to production by algae and yeast owing to its lower incubation time and simpler downstream processing. The physical parameters and medium composition were optimized for astaxanthin production by Paracoccus MBIC 01143. The optimized media was supplemented with tricarboxylic acid intermediates to enhance the pool of precursors, while the cofactors of Crt enzymes (ferrous sulphate, ascorbate, NADPH, ATP, and 2-oxoglutarate) were added to stimulate their enzyme activity aiming at higher astaxanthin accumulation. Malate at 5 mM and ferrous sulphate at 1 mM increased the astaxanthin production from 177 to 3,750 μg/L.
Mahesh V. Bule,Rekha S. Singhal 한국식품과학회 2011 Food Science and Biotechnology Vol.20 No.3
Ubiquinone-10 (CoQ10), a vitamin-like lipophilic component of the membrane-bound electron transport system, has a wide range of therapeutic, neutraceutical, and cosmeceutical applications. The objective of this study was to optimize nutritional requirements for production of CoQ10by Paracoccus dinitrificans NRRL B-3785 fermentation. Effect of type and concentration of carbon and nitrogen source on fermentation kinetic parameters were analyzed using logistic and Luedeking-Piret equations. In submerged batch fermentation, yield of CoQ10 was 12.22 mg/L when 40 g/L glycerol was used and specific growth rate (0.056/h) as well as growth associated constant (α=0.680 mg/g)were higher as compared to other concentrations. Ammonium nitrate and proteose peptone at 5 (α=0.677 mg/g; β=0.0072 mg/g·h) and 20 g/L (α=0.806 mg/g; β=0.0074 mg/g·h), respectively, were optimal for CoQ10 production. CoQ10 formation observed to be both growth and nongrowth associated. In optimized medium CoQ10 formation increased considerably from 1.91 to 14.12 mg/L.
( Bankar Sandip B. ),( Rekha S. Singhal ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.6
The growth kinetics of Streptomyces noursei NRRL 5126 was investigated under different aeration and agitation combinations in a 5.0 l stirred tank fermenter. Poly-ε-lysine biosynthesis, cell mass formation, and glycerol utilization rates were affected markedly by both aeration and agitation. An agitation speed of 300 rpm and aeration rate at 2.0 vvm supported better yields of 1,622.81 mg/l with highest specific productivity of 15 mg/l.h. Fermentation kinetics performed under different aeration and agitation conditions showed poly- ε-lysine fermentation to be a growth-associated production. A constant DO at 40% in the growth phase and 20% in the production phase increased the poly-ε-lysine yield as well as cell mass to their maximum values of 1,992.35 mg/l and 20.73 g/l, respectively. The oxygen transfer rate (OTR), oxygen utilization rate (OUR), and specific oxygen uptake rates (qO2) in the fermentation broth increased in the growth phase and remained unchanged in the stationary phase.
Ishwar B. Bajaj,Rekha S. Singhal 한국생물공학회 2010 Biotechnology and Bioprocess Engineering Vol.15 No.4
The effects of aeration and agitation on the production and molecular weight of poly (γ-glutamic acid)(PGA) were systematically investigated in batch fermentor cultures of Bacillus licheniformis NCIM 2324. A high aeration rate and agitation speed enhanced the growth of B. licheniformis NCIM 2324, but did not always lead to high PGA production. Additionally, PGA production actually decreased at very high aeration rates and agitation speeds. The maximum PGA concentration was obtained at 750 rpm and 1 vvm. Rheological studies revealed that fermentation broth during production of PGA exhibited pseudoplastic behavior. The effects of aeration and agitation on the molecular weight of PGA were also studied, and the rate and extent of the decrease in the molecular weight of PGA as a function of time were found to be much greater at high aeration than low aeration. The PGA production of 46.34g/L with a specific productivity of 0.17 g-PGA/g-biomass/h and a PGA yield of 0.48 with respect to total substrate observed in the present study are much higher than the values reported in previously conducted studies.
( Pansuriya Ruchir C. ),( Rekha S. Singhal ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.4
The effects of the agitation and aeration rates on the production of serratiopeptidase (SRP) in a 5-L fermentor (working volume 2-l) were systematically investigated using Serratia marcescens NRRL B-23112. The dissolved oxygen concentration, pH, biomass, SRP yield, and maltose utilization were all continuously measured during the course of the fermentation runs. The efficiencies of the aeration and agitation were evaluated based on the volumetric mass transfer coefficient (KLa). The maximum SRP production of 11,580 EU/ml with a specific SRP productivity of 78.8 EU/g/h was obtained with an agitation of 400 rpm and aeration of 0.075 vvm, which was 58% higher than the shake-flask level. The KLa for the fermentation system supporting the maximum production (400 rpm, 0.075 vvm) was 11.3 h-1. Under these fermentor optimized conditions, kinetic modeling was performed to understand the detailed course of the fermentation process. The resulting logistic and Luedeking-Piret models provided an effective description of the SRP fermentation, where the correlation coefficients for cell growth, SRP formation, and substrate consumption were 0.99, 0.94, and 0.84, respectively, revealing a good agreement between the model-predicted and experimental results. The kinetic analysis of the batch fermentation process for the production of SRP demonstrated the SRP production to be mixed growth associated.