Fed-Batch Bioproduction of Spectinomycin
J. Gomes* and A.S. Menawat**
* Department of Biochemical Engineering & Biotechnology,
Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India
** Advanced Solutions & Know-how, 1426, Hidden Creek North, Saline,
MI-48176, USA
Actinomycetes produce about 67% of the known antibiotics covering a wide range of chemical
structures. However, their filamentous growth present several problems during industrial processes.
Among these problems oxygen transfer limitation is critical. In this chapter we present the role of
oxygen in spectinomycin production by a Streptomyces species. Spectinomycin, a broad spectrum
antibiotic effective against penicillin resistant gonorrhea, is an aminoglycoside constituted from two
glucose moieties. Its bioproduction is strongly influenced by glucose and oxygen. We have shown
that for a fixed dissolved oxygen concentration, there are two specific glucose concentrations which
give maximum final titers of spectinomycin. The bi-modal maximum indicates the influence of two
intermediate metabolites in spectinomycin biosynthesis. We propose a mechanism for spectinomycin biosynthesis and subsequently develop a model based on this mechanism. The proposed
mechanism for spectinomycin biosynthesis is validated by successfully reconstructing the air flow
rate profiles. A nonlinear systems theory technique termed External Differential Representation, is
implemented to reconstruct the spectinomycin bioconversion process which then predicts the
spectinomycin concentration from the air flow rate profile. This signifies that spectinomycin titers in
industrial fed-batch processes can be controlled if a priori information about the air flow rate profile
yielding maximum spectinomycin is available.
List of Symbols and Abbreviations ..................................
2
1 Introduction .............................................
4
1.1 Physiology of Antibiotics ...................................
4
1.1.t Carbon Regulation ....................................
6
1.1.2 Nitrogen Regulation ...................................
6
1.1.3 Phosphate Regulation ..................................
7
2 Spectinomycin Biosynthesis .....................................
8
2.1 Organism and Metabolism ..................................
8
2.2 Role of Glucose and Oxygen .................................
10
3 Bioproduction of Spectinomycin ..................................
12
3.1 Preparation of Inoculum ....................................
12
3.2 Bioproduction Media ......................................
13
3.3 On-Line and Off-Line Analysis ................................
13
3.4 Spectinomycin Estimation ...................................
15
4 Fed-Batch Cultivation ........................................
17
4.1 Glucose Feed Optimization ..................................
17
4.2 Characteristics of Spectinomycin Bioproduction ......................
20
4.3 Influence of Residual Glucose Concentration ........................
21
4.4 Variations in Air Flow Rate ..................................
22
5 Two Metabolite Hypothesis ....................................
23
6 Exponential Structure for Mechanistic Model ..........................
25
6.1 Model Simulation ........................................
26
7 Prediction .............
..................................
31
7.1 External Differential Representation .............................
31
7.2 Air Flow Rate ..........................................
32
7.3 Spectinomycin ..........................................
36
Advances in Biochemical Engineering/
Biotechnology, Vol. 59
Managing Editor: Th. Scheper
9 Springer-Verlag Berlin Heidelberg 1998