Dynamic gene expression regulation model for growth and penicillin production in Penicillium chrysogenum

Abstract

As is often the case for microbial product formation, the penicillin production rate of Penicillium chrysogenum has been observed to be a function of the growth rate of the organism. The relation between the biomass specific rate of penicillin formation (q(p)) and growth rate (mu) has been measured under steady state conditions in carbon limited chemostats resulting in a steady state q(p)(mu) relation. Direct application of such a relation to predict the rate of product formation during dynamic conditions, as they occur, for example, in fed-batch experiments, leads to errors in the prediction, because q(p) is not an instantaneous function of the growth rate but rather lags behind because of adaptational and regulatory processes. In this paper a dynamic gene regulation model is presented, in which the specific rate of penicillin production is assumed to be a linear function of the amount of a rate-limiting enzyme in the penicillin production pathway. Enzyme activity assays were performed and strongly indicated that isopenicillin-N synthase (IPNS) was the main rate-limiting enzyme for penicillin-G biosynthesis in our strain. The developed gene regulation model predicts the expression of this rate limiting enzyme based on glucose repression, fast decay of the mRNA encoding for the enzyme as well as the decay of the enzyme itself. The gene regulation model was combined with a stoichiometric model and appeared to accurately describe the biomass and penicillin concentrations for both chemostat steady-state as well as the dynamics during chemostat start-up and fed-batch cultivation.

Comprehensive Profiling of Proteome Changes Provide Insights of Industrial Penicillium chrysogenum During Pilot and Industrial Penicillin G Fermentation

“…3), indicating that the industrial process may accelerate the high expression of IPN acyltransferase. Enzyme activity assays strongly indicated that isopenicillin-N synthase (IPNS) was the main rate-limiting enzyme for penicillin G biosynthesis [25]. Herein, we explored the dynamic changes in the intracellular proteomes associated with penicillin production of P. chrysogenum during the pilot and the industrial conditions.…”

Effect of phenolic compounds and osmotic stress on the expression of penicillin biosynthetic genes from Penicillium chrysogenum var. halophenolicum strain

“…10,22 Several groups have described that transcription of the genes encoding for the enzymes in the penicillin biosynthesis pathway is repressed by glucose. 9,[23][24][25] In P. chrysogenum, penicillin biosynthesis is repressed by glucose preventing expression of the pcbAB, pcbC and penDE genes. 25 According to published results, glucose induced not only higher rates of respiration but also greater energy production than lactose as carbon source in P. chrysogenum NRRL 1915 strain.…”

“…In other words, the expression level of pcbAB and penDE does not seem to be a relevant factor for antibiotic biosynthesis. Douma et al 24 reported that the control of penicillin biosynthesis is exerted by a single rate-limiting enzyme: the isopenicillin N synthase encoded by the pcbC gene. Meanwhile, other groups report that the rate limiting step reside either at δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine synthetase or at isopenicillin N synthase.…”

Linking genes to microbial growth kinetics—An integrated biochemical systems engineering approach

“…The enzymatic products of xylC (benzaldehyde dehydrogenase), xylM and xylA (xylene monooxygenase), and xylB (benzyl alcohol dehydrogenase) are involved in the oxidation of aromatic effectors to the corresponding benzyl alcohol, benzaldehyde, and benzoate respectively (Van Dien and de Lorenzo, 2003). Furthermore, it is widely accepted that control of the enzyme level on the flux of a pathway is distributed between all participating enzymes (Douma et al, 2010). Nevertheless, these enzymes do not exert the same level of control on the flux of the pathway, which is usually dominated by a single ratelimiting enzyme.…”

“…The current state of the art is rather limited to the recent work of Douma et al (2010) presenting the development of a simple dynamic gene regulation model to describe biomass and penicillin production in a chemostat. It was shown that although the gene regulation model was only validated using enzyme activity assays instead of measuring mRNA levels, it nevertheless improved significantly the prediction of the bioprocess demonstrating the benefits of accounting for genetic events in biochemical engineering.…”