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Improvement in Enzyme Productivities from Mold Cultivations Using the Liquid‐Phase Oxygen Supply Strategy
Author(s) -
Rawool Subodh B.,
Sahoo Susmita,
Rao K. Krishnamurthy,
Sureshkumar G. K.
Publication year - 2001
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp010078z
Subject(s) - aeration , aspergillus niger , catalase , oxygen , glucose oxidase , chemistry , limiting oxygen concentration , yield (engineering) , extracellular , chromatography , enzyme , biochemistry , materials science , organic chemistry , metallurgy
Cultivations of Aspergillus niger cells in which oxygen was provided through the liquid‐phase oxygen supply strategy (which involves the need‐based decomposition of H 2 O 2 pulses to yield the necessary oxygen) were studied. Concentrations of H 2 O 2 in the range of 1 to 5 mM were found to be suitable for use in cultivations. The growth rate constant of 0.17 h − 1 obtained in the H 2 O 2 ‐based cultivation, was comparable to that obtained in the cultivation with aeration; however, the maximum cell concentration in the H 2 O 2 ‐based cultivation was 124% of that obtained in cultivation with aeration. Maximum concentrations of catalase, protease and glucose oxidase obtained in the H 2 O 2 ‐based cultivation, were 240%, 172%, and 124% respectively, of those obtained in the cultivation with aeration. Further, the specific enzyme levels (units per gram cell) of catalase and protease obtained in the H 2 O 2 ‐based cultivation were 172% and 156% of those obtained in the cultivation with aeration, whereas, the specific glucose oxidase levels were comparable. In addition, the oxygen profiles inside the pellets of A. niger during both the modes of oxygen supply were described using mathematical models. Studies to elucidate the mechanism of oxygen availability showed that the decomposition of the H 2 O 2 supplied in the extracellular space occurred intracellularly, as well as extracellularly, to yield oxygen. Also, the proton motive force (PMF) was found to be involved in the process of oxygen availability from H 2 O 2 to A. niger cells.