Kinetics of improved productivity of β-galactosidase by a cycloheximide-resistant mutant of Kluyveromyces marxianus
ABSTRACT The maximum volumetric productivity of -galactosidase by a Kluyveromyces marxianus mutant, grown on lactose/corn steep liquor medium for 3d, was 150IUl–1h–1 which is twice that of the parent organism. During product formation, mutated cells provided more resistance against thermal inactivation.
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ABSTRACT: Detailed kinetic and thermodynamic parameters for lysine production from Brevibacterium lactofermentum are investigated for the first time in this study. Production of the essential amino acid, L-lysine, by B. lactofermentum was assessed in a flask and a continuously stirred tank fermentor (22 L). Maximum lysine production was achieved after 40 h of growth and at 35 °C. The effect of different nitrogen sources such as NH4NO3, (NH4)2SO4, (NH4)2HPO4, corn steep liquor, NaNO3, and urea showed that corn steep liquor gave a better lysine yield. Lysine production was increased when dissolved oxygen was maintained at 50 % saturation. The use of dissolved oxygen was critical for high productivity. This indicates that dissolved oxygen greatly affects L-lysine productivity. Kinetic and thermodynamic parameters during lysine production from molasses and glucose mixture showed that B. lactofermentum efficiently converted the substrate mixture into cell mass and lysine. Kinetic and thermodynamic parameters were significantly higher compared with other microorganisms which may be due to the high metabolic activity of B. lactofermentum. This study will have a significant impact on future strategies for lysine production at industrial scale.Applied biochemistry and biotechnology 03/2013; · 1.94 Impact Factor
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ABSTRACT: Seven strains of the genus Kluyveromyces were screened for β-galactosidase activity and Kluyveromyces marxianus ATCC 16045 was selected as the best enzyme producer for culture medium optimization. The production of β-galactosidase by submerged cultivation was evaluated using a factorial design and response surface methodology. The culture medium containing whey and parboiled rice effluent was formulated to maximize the production of β-galactosidase. The effects of the initial pH and the concentrations of whey lactose, peptone, (NH4)2SO4, yeast extract, and parboiled rice effluent on enzyme production were studied using a 2IV6-2 fractional design. A CCRD (24 trials plus axial and central points) was used for the four variables selected from the fractional design (lactose, peptone, (NH4)2SO4 and yeast extract), with β-galactosidase activity as the response. The optimum conditions established for production were a whey (lactose) concentration of 120g/L, a yeast extract concentration of 5g/L, a peptone concentration of 15g/L, a (NH4)2SO4 concentration of 15g/L, a parboiled rice effluent concentration of 30g/L, and a pH value of 4.0. Under these conditions, the highest enzymatic activity of 10.4U/mL was measured, being 9.5–9.7 as the values predicted by the proposed model, showing an enzymatic activity increase of 30% using alternative sources of lactose and nitrogen for β-galactosidase production. KeywordsExperimental design–Galactosidase–Parboiled rice effluent–RSM–WheyFood and Bioprocess Technology 07/2011; · 3.13 Impact Factor
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ABSTRACT: Industrial byproducts namely canola meal, rice bran, sunflower meal, and wheat straw were used as substrates for endo-xylanase production by Humicola lanuginosemutant TH1 through solid substrate fermentation. The enzyme was secreted extracellularly by both wild and mutant cultures. Rice bran supported the maximum production of endo-xylanase followed by wheat straw, canola meal and sunflower meal. The highest activity was achieved after 72 h of culture and the highest yields from the above substrates were 842, 840, 610 and 608 IU per g substrate consumed respectively. The highest productivity (281 IU flask−1 h−1 corresponding to 5620 l−1 h-1) of endo-xylanase by the mutant of H. lanuginosa was 1.6-fold more than that produced by the parental organism in solid-state fermentation of rice bran at 45 °C. Maximum specific activity (180 IU mg−1 protein) and substrate consumption rates were significantly more than those reported by previous researchers on Humicola sp. The mutant possessed markedly low accompanying cellulase activity. Thermodynamic studies revealed that the mutant required significantly lower activation energy for enzyme production and higher for thermal inactivation which signified that the endogenous metabolic machinery of mutant cells exerted more protection against thermal inactivation during product formation than that needed by its parental cultures.World Journal of Microbiology and Biotechnology 09/2005; 21(6):869-876. · 1.35 Impact Factor