Maximization of intracellular lipase production in a lipase-overproducing mutant derivative of Rhizopus oligosporus DGM 31: a kinetic study

Regulation and maximization of lipase production in a mutant derivative of R. oligosporus has been investigated using different substrates, inoculum sizes, pH of the medium, temperature, and nitrogen sources in shake flask experiments and batch fermentation in a fermentor. The production of intracel...

Full description

Saved in:
Bibliographic Details
Published in:Food technology and biotechnology 2008-10, Vol.46 (4), p.402-412
Main Authors: Iftikhar, Tehreema, Niaz, Mubashir, Afzal, Munazza, Rajoka, Muhammad Ibrahim
Format: Article
Language:English
Subjects:
Enzymatic analysis
Fermentation
Fungi
glycerol
Immobilized enzymes
Lipase
lipases
nitrogen sources
oils
Production processes
Rhizopus oligosporus
starch
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Regulation and maximization of lipase production in a mutant derivative of R. oligosporus has been investigated using different substrates, inoculum sizes, pH of the medium, temperature, and nitrogen sources in shake flask experiments and batch fermentation in a fermentor. The production of intracellular lipase was improved 3 times following medium optimization involving one-at-a-time approach and aeration in the fermentor. Interestingly, intracellular lipase was poorly induced by oils, instead its production was induced by sugars, mainly starch, lactose, sucrose, xylose, glucose and glycerol. Dependent variables studied were cell mass, lipase activity, lipase yield, lipase specific and volumetric rate of formation. It was confirmed that lipase production in the derepressed mutant is sufficiently uncoupled from catabolite repression. The results of average specific productivities at various temperatures worked out according to the Arrhenius equation revealed that mutation decreased the magnitude of enthalpy and entropy demand in the inactivation equilibrium during product formation, suggesting that mutation made the metabolic network of the organism thermally more stable. The highest magnitudes of volumetric productivity ([Q.sub.P]=490 IU/(L*h)) and other product attributes of lipase formation occurring on optimized medium in the fermentor are greater than the values reported by other workers. The purified enzyme is monomeric in nature and exhibits stability up to 80 °C and pH=6.0-8.0. Activation energy, enthalpy and entropy of catalysis at 50 °C, and magnitudes of Gibbs free energy for substrate binding, transition state stabilization and melting point indicated that this lipase is highly thermostable. Key words: lipases, Rhizopus oligosporus, oils, casein, ammonium nitrate, ammonium oxalate, starch, glycerol
ISSN:1330-9862
1334-2606