Metabolic flux analysis for serine alkaline protease fermentation by Bacillus licheniformis in a defined medium: Effects of the oxygen transfer rate

Çalık, Pınar
Ozdamar, TH
The metabolic fluxes through the central carbon pathways in the bioprocess for serine alkaline protease (SAP) production by Bacillus licheniformis were calculated by the metabolic flux-based stoichiometric model based on the proposed metabolic network that contains 102 metabolites and 133 reaction fluxes using the time profiles of citrate, dry cell, organic acids, amino acids, and SAP as the constraints. The model was solved by minimizing the SAP accumulation rate in the cell, The effects of the oxygen-transfer rate (OTR) on the metabolic fluxes were investigated in a defined medium where citrate was used as the sole carbon source. The centra I pathways were active for the growth and the SAP synthesis in all the periods of the bioprocess at low (LOT), medium (MOT), and high (HOT) oxygen-transfer conditions. The flux partitioning in the TCA cycle at alpha-ketoglutarate towards glutamate group and at oxalacetate (OA) toward aspartic acid group amino acids were dependent on the OTR. The flux of the anaplerotic reaction that connects the TCA cycle either from malate or OA to the gluconeogenesis pathway via the main branch point pyruvate (Pyr) was also influenced by the OTR. With the decrease in the OTR, the intracellular flux values after glycerate 3-phosphate (PG3) in the gluconeogenesis pathway and the specific growth rate decreased. The total ATP-generation rate increased with the increase in OTR. The pathway towards the aspartic acid family amino acids which is important for sporulation that precedes the SAP synthesis were all active throughout the bioprocess. Metabolic flux analysis results at LOT, MOT, and HOT conditions encourage the design of an oxygen-transfer strategy in the bioreactor; moreover, asparagine synthetase or aspartate kinase could be the potential metabolic engineering sites due to the low value of the flux from the branch point aspartate toward asparagine. (C) 1999 John Wiley & Sons, Inc.


Metabolic flux analyses for serine alkaline protease production
Çalık, Pınar; Ozdamar, TH (2000-12-01)
The intracellular metabolic fluxes through the central carbon pathways in Bacillus licheniformis in serine alkaline protease (SAP) production were calculated to predict the potential strategies for increasing the performance of the bacilli, by using two optimization approaches, i.e. the theoretical data-based (TDA) and the theoretical data-based capacity (TDC) analyses based on respectively minimum in-vivo SAP accumulation rate and maximum SAP synthesis rate assumptions, at low-, medium, and high-oxygen tra...
Metabolic network analysis for human therapeutic protein productions: Effects of the P/O ratio
Çalık, Pınar (2000-10-08)
The metabolic fluxes through the central carbon pathways in the bioprocesses for human leukocyte interferon (IFN-alpha(1)) and erythropoietin (EPO) overproductions by recombinant Bacillus sp, carrying the related human genes were determined separately, on two alternative carbon sources, i.e. glucose and citrate, which have different reduction degrees. In addition, the influence of the P/O ratio on the cell growth, IFN-alpha(1) and EPO productions were investigated. Thus, the potential influence of increased...
Bioprocess development for serine alkaline protease production: A review
Çalık, Pınar; Ozdamar, TH (2001-01-01)
This work is the result of the convergence of the research in biochemical reaction engineering and metabolic flux analysis for serine alkaline protease (SAP) production. The genus Bacillus includes a variety of industrially important species that are known to secrete a large number of extracellular proteases and are used among many species as producer of SAP enzyme. Therefore, in the first part of the present article an overview to serine alkaline protease and regulation of its synthesis and secretion in Ba...
Serine alkaline protease overproduction capacity of Bacillus licheniformis
Çalık, Pınar; Ozdamar, TH (2000-01-01)
A comprehensive metabolic network that considers 147 reaction fluxes and 105 metabolites is used in a mass-Aux-balance-based stoichiometric model for Bacillus licheniformis for serine alkaline protease (SAP) overproduction. The theoretical capacity analysis leading to optimized SAP overproduction was carried out by using a linear constrained optimization technique for several specific growth rates and the variation of the fluxes were calculated by fixing the sole carbon source citrate's uptake rate at 10 mm...
Oxygen-transfer strategy and its regulation effects in serine alkaline protease production by Bacillus licheniformis
Çalık, Pınar; Özdamar, Tunçer H. (2000-08-01)
The effects of oxygen transfer on the production and product distribution in serine alkaline protease (SAP) fermentation by Bacillus licheniformis and oxygen-transfer strategy in relation to the physiology of the bacilli were investigated on a defined medium with citric acid as sole carbon source in 3.5-dm(3) batch bioreactor systems. By forming a 3 x 3 matrix with the parameters air-inlet rates of Q(O)/V-R = 0.2, 0.5, 1.0 vvm, and agitation rates of N = 150, 500, 750 min(-1), the effects of oxygen transfer...
Citation Formats
P. Çalık and T. Ozdamar, “Metabolic flux analysis for serine alkaline protease fermentation by Bacillus licheniformis in a defined medium: Effects of the oxygen transfer rate,” BIOTECHNOLOGY AND BIOENGINEERING, pp. 151–167, 1999, Accessed: 00, 2020. [Online]. Available: