Michel M. Chartrain

Purification and characterization of a novel bioconverting lipase from Pseudomonas aeruginosa MB 5001

Abstract The purification and characterization of a lipase produced by Pseudomonas aeruginosa strain MB 5001 that was selected for its unique bioconversion properties is described herein. The purified lipase bioconverts dimethyl 5-(3-(2-(7-chloroquinolin-2-yl)-ethyl)phenyl)4, 6-dithianonanedioate (diester) to its (S)-ester acid, an intermediate in the synthesis of Verlukast, a leukotriene receptor antagonist. In its native form, the enzyme exists as high-molecular-weight aggregates that are dissociated with Triton X-100. The purified enzyme has a molecular weight of 29,000 daltons, a pH optimum of 8.0, a temperature optimum of 55°C, and is stable for 1 h at 40°C. This lipase is strongly inhibited by 1 m m ZnSo 4 (94% inhibition) but is stimulated by the addition of 10 m m CaCl 2 (1.24-fold) and 200 m m taurocholic acid (1.6-fold). It is more active on short-chain versus long-chain triglycerides, and hydrolyzes C18-unsaturated fatty acid esters more efficiently than it hydrolyzes C18-saturated fatty acid esters. In light of its catalytic and physicochemical properties, this enzyme is regarded as a novel lipase .

Development of a defined medium fermentation process for physostigmine production by Streptomyces griseofuscus

Physostigmine is a plant alkaloid of great interest as a therapeutic candidate for the treatment of Alzheimers disease. Fortunately, this compound is also produced by Streptomyces griseofuscus NRRL 5324 during submerged cultivation. A fermentation process that used chemically defined medium was therefore developed for its production. By means of statistical experimentation, the physostigmine titer was quickly increased from 20 mg/l to 520 mg/l with a culture growth of 19 gl dry cell weight on the shake-flask scale. Further medium optimization resulted in a yield of 790 mg/l in a 23-l bioreactor using a batch process. A titer of 880 mg/l was attained during scale-up in a 800-l fermentor by employing a nutrient-feeding strategy. This production represents a 44-fold increase over the yield from the initial process in shake-flasks. The defined-medium fermentation broth was very amenable to downstream processing.

Conversion of indene to cis-(1S),(2R)-indandiol by mutants of Pseudomonas putida F1

Two mutation and selection methods were used to isolate mutants of Pseudomonas putida F1 which convert indene to cis-(1S),(2R)-indandiol in a toluene-independent fashion. Using soybean or silicone oil as a second phase to deliver indene to the culture, cis-(1S),(2R)-indandiol, cis-(1R),(2S)-indandiol, 1,2-indenediol (or the keto-hydroxy indan tautomer), and the monooxygenation products 1-indenol and 1-indanone were produced from indene as a function of time. Similarly the enantiomeric excess of the cis-(1S),(2R)-indandiol produced also increased with increasing time. In addition, mutants were isolated which produced cis-(1S),(2R)-indandiol of lower optical purity which corresponded to reduced levels of 1,2-indenediol. These data suggest this toluene dioxygenase produces cis-(1S),(2R)-indandiol of low optical purity and that cis-glycol dehydrogenase plays a role in resolving the two cis-1,2-indandiol enantiomers.

Optimization of lipase production byPseudomonas aeruginosa MB 5001 in batch cultivation

SummaryThe production ofPseudomonas aeruginosa MB 5001 extracellular lipase was optimized by batch cultivation employing shake flasks and 23-L bioreactors. This enzyme efficiently and selectively bioconverts dimethyl 5-(3-(2-(7-chloroquinolin-2-yl)ethyl)phenyl)4,6-dithianonanedioate (diester) to its (S)-ester acid. Process development studies focused on the identification and optimization of the physicochemical parameters required to achieve maximum lipase production. Of the media evaluated, a peptonized milk-based medium was found to support excellent lipase production and stability. Medium composition and process parameters that supported optimal lipase production were different from those supporting maximum biomass formation. Of the parameters investigated, dissolved oxygen tension had the most significant and unexpected impact on lipase production. Elevated lipase production was achieved whenP. aeruginosa MB 5001 was cultivated in a dissolved oxygen limited environment. Overall, these process development studies resulted in a 100% increase in lipase production when compared to the original shake flask process employing skim milk.

Evaluation of an electrochemical bioreactor system in the biotransformation of 6-bromo-2-tetralone to 6-bromo-2-tetralol.

Abstract. Biotransformation of 6-bromo-2-tetralone (Br-β-tetralone) to 6-bromo-2-tetralol (Br-β-tetralol) by yeast cells of Trichosporon capitatum (ATCC 74312) and its partially purified Br-β-tetralone reductase was evaluated in an electrochemical bioreactor. The biotransformation rates and final product formation were significantly affected by substrate concentration, biomass and electric potential. At 2xa0g/l of substrate, the initial reaction rate and final product were increased by 35% and 15%, respectively, with –1.5xa0V of electric potential compared to without electric potential. Additional substrate (2xa0g/l) provided by pulse feeding to the reaction mixture at different intervals resulted in 2.1xa0g/l Br-β-tetralol compared to a total of 1.2xa0g/l without feeding. However, the increased production was not proportionate to the amount of additionally fed substrate. Increased substrate availability by the addition of 5% (v/v) ethanol resulted in the highest reaction rate and product formation, but addition of ethanol at a concentration higher than 5% decreased the reaction rate. At low biomass, the initial reaction rates were enhanced significantly when electric potential was high, but a higher biomass was necessary to obtain a similar reaction rate when electric potential was reduced. The highest initial reaction rate (59.2xa0mg/l per min) was achieved with a two-fold biomass concentration of 15.6xa0g of dry cell weight/l, substrate at 4xa0g/l and electric potential at –6xa0V. The conversion of Br-β-tetralone to Br-β-tetralol with partially purified Br-β-tetralone reductase was slow in the presence of electric potential.

Bioconversion of indene to trans-2S,1S-bromoindanol and 1S,2R-indene oxide by a bromoperoxidase/dehydrogenase preparation from Curvularia protuberata MF5400

Abstract 1S,2R-Indene oxide is the precursor of cis -1S,2R-aminoindanol, a key intermediate for the Merck HIV–1 protease inhibitor, Crixivan®. As an alternative to the challenging chemical synthesis of this chiral epoxide from indene, the biotransformation route using an enzyme catalyst was examined. Approximately 3% of the 400 fungal cultures isolated from high salt environments were found to possess neutral haloperoxidase activities. Subsequent studies revealed that indene conversion by these positive cultures could only be obtained when both hydrogen peroxide and bromide ions were present. The products were generally racemic trans -bromoindanols which upon basification yielded racemic epoxides. Finally, it was found that a crude enzyme preparation from the fungal culture Curvularia protuberata MF5400 converted indene to the chiral 2S,1S-bromoindanol which can be chemically converted to the desired 1S,2R-epoxide through basification or used directly in the asymmetric synthesis of cis -1S,2R-aminoindanol. The bioconversion rate and the enantiomeric excess (ee) achieved with this cell-free system were heavily pH dependent. An initial 1.5-h reaction at pH 7.0 gave ∼10% yield of the chiral bromoindanol or epoxide from indene, and the yield was rapidly improved to >30% for trans -2S,1S-bromoindanol with an ee of 80%. Reaction mechanistic studies revealed that the stereoselectivity observed was apparently due to a specific dehydrogenase activity present in MF5400 which was also found to resolve chemically synthesized racemic trans -2-bromoindanols.

Development of crossflow filtration processes for the commercial-scale isolation of a bacterial lipase

Isolation of a lipase produced by Pseudomonas aeruginosa (MW 29,000) employed crossflow microfiltration for production of a cell-free enzyme solution and crossflow ultrafiltration for concentration of the enzyme and removal of low molecular weight impurities. Poor flux and enzyme permeation were measured during initial screening of various microfiltration membrane types for isolation of the enzyme from a peptonized-milk-based broth; the results suggested that a soluble broth component was forming a gel layer which controlled both hydraulic flux and enzyme permeation. Reformulation of the fermentation medium resulted in enhanced performance, obtaining fluxes of 40 l/h m2 and enzyme permeation of 50% on hydrophilically-modified PVDF membranes and resulted in a feasible clarification process. Enzyme permeation remained constant with respect to activity in the feed, rather than being proportional to activity in the retentate; it was hypothesized that this resulted from a concomitant concentration of the gel-forming components with cell concentration. Concentration of the clarified enzyme solution was performed using 30 000 MWCO regenerated cellulose membranes. Complete enzyme retention and high flux (57 l/h m2) were maintained through a 130-fold concentration of the microfiltrate. As both systems were taken to the 100 and 1000 l scales, similar filtration performances were obtained with system hold-up volume and pump cavitation becoming important considerations at the larger scales. Excellent reproducibility was observed in a series of eight large-scale experiments.

Design-for-Six-Sigma for Development of a Bioprocess Quality-by-Design Framework

An initial quality-by-design (QbD) framework was assembled for biopharmaceutical product, process, and analytical development using the design-for-six-sigma (DFSS) methodology. This technique was both streamlined and efficient, which permitted development of a QbD framework with minimized team leader and member resources. DFSS also highly emphasized voice-of-the-customer, information considered crucial to development and implementation of a bioprocess QbD framework appropriate for current development needs of the organization and its regulatory environment. The bioprocess QbD final design and implementation plan was comprised of seven teams, constructed from six QbD elements plus a communication/training team. Each elements detailed design was evaluated against internal and external established best practices, the QbD charter, and design inputs. Gaps were identified and risks mitigated to assure robustness of the proposed framework. Aggregated resources and timing were estimated to obtain vital implementation sponsorship. Where possible, existing governance and information technology efforts were leveraged to minimize additional bioprocess resources required. Finally, metrics were selected to track success of pilots and eventual implementation. LAY ABSTRACT: An initial quality-by-design (QbD) framework was assembled to guide biopharmaceutical product, process, and analytical development. QbD starts by defining the patient requirements which then are translated into required quality attributes for the product. The production process then is designed to consistently meet these quality requirements by identifying and understanding those parameters which influence them. A control strategy is developed that specifically relates each point of control to a desired quality measure. Overall, this approach results in a robust process, capable of reliably producing quality product. The bioprocess QbD framework was developed to guide implementation of the desired QbD strategy. It was comprised of seven teams, constructed from six QbD elements plus a communication/training team. Each elements detailed design was evaluated against internal and external established best practices, the charter, and design inputs. Gaps were identified and risks mitigated to assure robustness of the proposed framework. Aggregated resources and timing were estimated to obtain vital implementation sponsorship. Where possible, existing governance and information technology efforts were leveraged to minimize additional bioprocess resources required. Finally, metrics were selected to track success of pilots and eventual implementation.

Bioconversion of avermectin into 27-OH avermectin

SummaryThe bioconversion of avermectin to its 27-hydroxy derivative is achieved withNocardia autotrophica subsp.canberrica. The approach of increasing bioconversion productivity rather than efficiency was adopted in these studies. Process improvement studies focused on the physico-chemical conditions of the fermentation, examined initially at the shake-flask scale. Bioconversion yields were affected by pH, substrate concentration, time of substrate addition, substrate solubilization, carbon to nitrogen ratio, and medium strength. Optimization of these parameters resulted in a 8-fold process improvement. During pre scale-up studies, the sensitivity of this bioconversion to the antifoam employed was demonstrated and lard oil was selected as giving the best results. Additional process changes were required during scale-up efforts in larger vessels, including replacement of the original substrate solvent with dimethylsulfoxide.

Automatic whole broth multi-fermentor sampling

SummaryAn efficient, aseptic method of obtaining whole broth fermentation samples was developed based on a piston-valve, a local sample loop, and an ability to drive the entire sample volume with sterile air through a sample line and into a remote tube. The configuration delivers 10-ml samples 10 m away with about 4 ml of broth wasted in the sampling process. An autosampler was enhanced and programmed to control acquisition into chilled tubes. The autosampler-based system represents a convenient way to provide frequent samples to profile intracellular and extracellular components for yeast and bacterial fermentations. A configuration to provide sampling from six fermentors with a multi-rack autosampler will be presented.