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Through the analysis of the inhibitory effect on HMGCoA reductase, it is possible to highlight the influence of the obtained structures on biological activity. Various fungi such as Aspergillus (A. Uncontrolled filamentous growth occurs when using rapidly metabolized substrates.
The rapid increase in viscosity accompanied by filamentous growth greatly impedes oxygen transfer and this is said to explain the low titers of lovastatin. Fermentationderived lovastatin is a precursor for simvastatin, a powerful semi-synthetic statin commercially available as ZocorTM. Simvastatin is obtained via a selective enzymatic deacylation of lovastatin8. An alternative method for the lovastatin synthesis was semi-synthetic route where the synthesis occurs via the regioselective enzymatic esterification of 2-methylbutyric acid and a diol lactone precursor.
The method has the potential advantage that different analogs of lovastatin can be synthesized from the same lactone precursor using different carboxylic acids. Lovastatin also inhibits tumor growth through the inhibition of non-sterol isoprenoid synthesis. Lovastatin (mevinolin) was the first hypocholesterolemic drug to be approved by Food and Drug administration (FDA), USA. Submerged batch fermentation of lovastatin production was reported in various literatures and commercial production of lovastatin is based on A.
Batch fermentation generally runs for less than 10 days. In some cases, pelleted growth of A. The composition of a fermentation medium influences the supply of nutrients and metabolism of cells in a bioreactor and therefore the productivity of a fermentation process depend on the culture medium used.
Also, the nature and concentration of the carbon source can regulate secondary metabolism through phenomena such as catabolic repression. Response surface methodology (RSM) was also adapted in identifying the impact of the medium composition on lovastatin production with a high producing A.
No report exists on any interactive effects of dissolved oxygen and the other nutrients on the production of lovastatin.
Process optimization is a tedious process due to involvement of multivariable process parameters. Screening of important factors is initially carried out and the selected factors are then optimized by different techniques.
Fed-batch fermentations of A. Submerged fermentation processes for large-scale lovastatin production have been developed using A. Solid state fermentation uses economical substrates (agricultural residues), requires fewer processing and down-streaming stages, utilizes lesser power and generates lesser effluent. Moreover, SSF has higher product yield and offers better product stability.
Because of the reasons, solid state fermentation was used mainly for the production of industrial enzymes but nowadays, it is also being exploited for the production of secondary metabolites. However, there is no discussion in the literature of how the concentration of lovastatin might affect its own synthesis by A. Subsequent experiments employing the cell-free extract of M. The monacolin X, i.
The investigation of the biogenesis of lovastatin, carried out mainly in Aspergillus terreus strains employing labeled precursors indicated that the lovastatin biosynthetic pathway starts from acetate units (4- and 8-carbons long) linked to each other in head-to-tail fashion to form two polyketide chains. The methyl group present in some statins in the side chain or at C6 derives from methionine, as frequently occurs in fungal metabolism, and is inserted in the structure before the closure of the rings.
Studies on the 13C incorporation in lovastatin carried out with Penicillium citrinum and M. More-recent investigations have studied the enzymatic kinetics together with gene regulation and expression involved in A.
The genetic research investigated the mechanisms involved in lovastatin biosynthesis, particularly with regard to the two polyketide chains. The results, including the characterization of A. Study of the primary structure of the PKS that forms the lovastatin nonaketide provided new details of lovastatin biosynthesis. Other aspects of the biosynthesis of lovastatin related to PKSs have been investigated. The LNKS, product of lovB gene, interacts with lovC (a putative enoyl reductase), to catalyze the reactions in the first part of the biosynthetic pathway, leading to dihydromonacolin L.
In the final step of the lovastatin pathway, the LDKS, made by lovF, interacts with lovD (transesterase enzyme) that catalyzes the attachment of the 2-methylbutyric acid to monacolin J, derived from monacolin L. Key features of genes encoding these enzymes and regulatory factors in lovastatin production in A.
An intramolecular Diels-Alder endo closure of the hexaketide, to form a bicyclic system, with the same ring stereochemistry as dihydromonacolin L, catalyzed by LNKS purified from A. Finally in a strain of A. The results demonstrated that the role of the lovC protein is to ensure correct assembly of the nonaketide chain in lovastatin by the lovB protein. In contrast, the construction of the methylbutyrate side chain by the LDKS (lovF protein) does not require lovC protein.
The detailed process of biosynthesis of lovastatin is shown in fig. Figure 3: Biosynthesis of lovastatin The lovastatin biosynthetic pathway starts from acetate units linked to each other in head- to-tail fashion to form two polyketide chains. The investigations carried out since 1970s have indicated the possibility of obtaining a wide range of lovastatin as both the final products and intermediates of secondary microbial metabolism, or as products of biotransformation process.
Largescale processes have been developed only for a few of the lovastatin described in the literature. For other molecules research is still ongoing and therefore greatly susceptible to future development.
However, mevastatin was the first statin discovered. Lovastatin (named mevinolin) was later obtained from a strain isolated from soil and classified as A. A few years later, lovastatin was also obtained from 17 strains of different species of 124 tested strains of the genus Monascus, in particular M.
The genus Monascus, particularly the species M. Studies on the synthesis and characterization of the lovastatin-related compounds indicated that several monacolins were obtainable, mostly from Monascus strains. Monacolin J and L were isolated and characterized from cultures of an M. In 1985, Endo has reported dihydromonacolin L and monacolin X production and activity from a mutant strain of M. A series of statins were also obtained by chemical modification of the C8 side chain in the lovastatin molecule and a systematic evaluation of the structure-activity relationships of the obtained compounds was also carried out.
The industrial process for the production of lovastatin was set up in 1980 using an A. The process development involved the analysis of different fermentation parameters such as culture homogeneity, effect of various carbon sources, pH, aeration, and agitator design. Scaling-up of the process from an 800 l to a 19,000 l scale revealed that oxygen transfer, related to high viscosity of the fermentation broth, is a serious limiting factor in lovastatin productivity.
Metkinen group (The original lovastatin producer) increased the lovastatin production by A. Biocon (Biocon India, Bangalore, India) is one of the companies that have obtained US FDA approval for lovastatin production (January 2001), and patented in June 2001.
The production of biomass and lovastatin by sporeinitiated submerged fermentations of Aspergillus terreus ATCC 20542 was studied and shown that the production depends on the age of the spores used for inoculation and the lovastatin titer was found to be 186. The optimized fermentation conditions raised the lovastatin titer by four-fold compared with the worstcase scenario within the range of factors and this study was also investigated that the culture medium had excess carbon but limiting amounts of nitrogen source for the better productivity.
This study used statistical analysis in documenting the interactions between oxygen supply and nutrient concentrations in lovastatin production. Accumulation of lovastatin suppresses its own synthesis in the microfungus Aspergillus terreus through a feed back regulatory mechanism and hence the product was removed continuously from the production medium.
A cost effective repeated fed-batch process with maltodextrin and corn steep liquor feed as carbon and nitrogen sources, respectively, showed a significant increase in lovastatin yield. The maximum specific oxygen uptake rate (QO2) and volumetric mass transfer coefficient (KLa) were 0.
Homogenity and stability of high producing strain of Aspergillus terreus, the rate of utilization of the carbon source, pH control and high level of dissolved O2 tension (DOT) are of essential importance for high lovastatin production. Among several organic and inorganic defined nitrogen sources metabolized by A.
For cultures on glucose and glutamate, lovastatin synthesis initiated when glucose consumption leveled off. A lovastatin-hyperproducing culture of Aspergillus terreus has shown to produce several co-metabolites extracted from whole broth.