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Effects of pH Strategy on endo ‐ and exo ‐Metabolome Profiles and Sodium Potassium Hydrogen Ports of β‐Lactamase‐Producing Bacillus licheniformis
Author(s) -
İleri Nazar,
Çalik Pinar
Publication year - 2006
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/bp050373+
Subject(s) - bacillus licheniformis , chemistry , extracellular , antiporter , lactic acid , biochemistry , intracellular , symporter , acetic acid , sodium , intracellular ph , chromatography , nuclear chemistry , bacteria , membrane , biology , organic chemistry , genetics , transporter , bacillus subtilis , gene
Abstract The effects of pH strategy on endo ‐ and exo ‐metabolome profiling of β‐lactamase‐producing Bacillus licheniformis were investigated at controlled‐pH (pH C = 6.5, 6.75, 7.0, 7.25, 7.5) and uncontrolled‐pH (pH UC = 7.5) values using a glucose‐based defined medium. The cell concentration profiles were not affected by the pH considerably within the investigated range. The highest enzyme activities were obtained as A = 54 U cm −3 at pH C = 6.75 among the controlled‐pH operations and as A = 57 U cm −3 at the uncontrolled‐pH pH UC = 7.5. At all conditions, oxygen transfer resistances were more effective, whereas the limitation increased in the β‐lactamase production phase. Total intracellular amino acid concentrations ranged between 0.142 and 6.766 kg m −3 (0.0058–0.277 g g cell −1 ), and their concentrations in terms of kg m −3 were, at most, 580‐fold higher than the extracellular concentrations. Methionine/cysteine concentrations were generally higher than the other intracellular amino acids, whereas asparagine concentration was the highest in the fermentation broth. From Na + , K + , and H + ion profiles, Na + ‐K + antiport and Na + ‐H + symport were found to be present within the system, and a correlation was found between organic acid transport and Na + ‐H + symport. Intracellular organic acid concentrations in terms of kg m −3 were, at most, 20‐fold higher than that of the extracellular, and with the increase in pH, extracellular acetic acid concentration increased and lactic acid concentration decreased. Average permeability coefficient values of organic acids were found to be in the range from 4.10 × 10 −7 to 4.32 × 10 −6 cm s −1 for the growth phase (0 < t < 6 h) and decreased at least 3‐fold in the β‐lactamase production phase (8 < t < 15 h), indicating the considerable structural change of the lipid membrane during the fermentation.