Bioprocess design parameters for beta-lactamase production by Bacillus species

Çelik, Eda
In this study, the effects of bioprocess design parameters on β-lactamase production were systematically investigated using wild type Bacillus species. For this purpose, the research programme was carried out in mainly four parts. Initially, potential β-lactamase producers were screened and Bacillus licheniformis ATCC 25972, a constitutive β-lactamase producer, was selected. Next, the effects of bioprocess medium components, i.e., carbon sources (glucose, fructose, sucrose, citric acid and glycerol), inorganic nitrogen sources ((NH4)2HPO4 and NH4Cl) and organic nitrogen sources (yeast extract, peptone and casamino acids), were investigated in agitation and heating rate controlled laboratory scale bioreactors. Thereafter, by using the designed medium, the effects of bioprocess operation parameters, i.e., pH and temperature, on β- lactamase activity were investigated in order to achieve a higher β-lactamase production. Among the investigated bioprocess conditions, the highest β- lactamase activity was obtained as 275 U cm-3, in the medium with 10.0 kg m-3 glucose, 1.2 kg m-3 (NH4)2HPO4, 8.0 kg m-3 yeast extract and the salt solution, at pH0=6.0, T=32°C, N=200 min-1, which was 7.9 fold higher than the activity obtained in the reference medium. Finally, using the optimum bioprocess parameters obtained in laboratory scale experiments, the fermentation and oxygen transfer characteristics of the bioprocess were investigated in 3.0 dm3 pilot scale bioreactor, having temperature, pH, foam and stirring rate controls, at Q0/V=0.5 vvm and N=500 min-1 oxygen transfer conditions. The variations in β- lactamase activity, cell, glucose, amino acid and organic acid concentrations with the cultivation time; the oxygen uptake rate and the liquid phase mass transfer coefficient values were determined. Throughout the bioprocess, overall oxygen transfer coefficient (KLa) varied between


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Citation Formats
E. Çelik, “Bioprocess design parameters for beta-lactamase production by Bacillus species,” M.S. - Master of Science, Middle East Technical University, 2003.