<i>Rhodococcus rhodochrous </i>strain and use thereof in the production of acrylic acid

Abstract

A strain of Rhodococcus rhodochrous in which a gene coding at least part of a nitrile hydratase enzyme or any gene coding a protein involved in the transcription, translation or formation of at least part of the nitrile hydratase enzyme has been deactivated or rendered ineffective or a strain of Rhodococcus rhodochrous cultured under condition wherein the nitrile hydratase enzyme is been inhibited.

Claims

1. A strain of Rhodococcus rhodochrous having been deposited under NCIMB Accession Number 42803.

2. The strain of claim 1, wherein the strain expresses a nitrilase enzyme which is capable of catalyzing the conversion of acrylonitrile to acrylic acid at concentrations of acrylonitrile exceeding 175 mM.

3. The strain of claim 1, wherein the strain is cultivated in the presence of isobutyronitrile to inhibit nitrile hydratase activity.

4. The strain of claim 1, wherein the strain is cultivated in the presence of ε-caprolactam to induce production of nitrilase.

5. A method for converting acrylonitrile to acrylic acid, the method comprising: (a) cultivating a strain of Rhodococcus rhodochrous having been deposited under NCIMB Accession Number 42803 in a growth medium containing ε-caprolactam and isobutyronitrile; (b) adding acrylonitrile; and (c) converting acrylonitrile to acrylic acid; wherein the conversion of acrylonitrile to acrylic acid is catalyzed by nitrilase produced by the Rhodococcus rhodochrous strain.

6. The method of claim 5, wherein the concentration of acrylonitrile exceeds 175 mM.

7. The method of claim 5, wherein the ε-caprolactam induces production of nitrilase.

8. The method of claim 5, wherein the isobutyronitrile inhibits nitrile hydratase activity.

Description

DETAILED DESCRIPTION

(1) A strain of Rhodococcus rhodochrous identified as NCIMB 42803 is cultivated in a growth medium, (containing g/L to 6 g/L ε-caprolactam) at 30° C. to 40° C. for 120 hours (5 days) in 300 mL conical flask. Inhibition of nitrile hydratase produced by the Rhodococcus rhodochrous strain is achieved by adding 2 g/L to 10 g/L of isobutyronitrile. The process is up-scaled to a 3 L volume in a Sarorius 5 L glass bioreactor for a larger yield of enzyme and cell production for use in a bioconversion application.

(2) Bioreactions are performed in a bioreactor at 1 L volumes in which acrylonitrile is added to a reactor containing water and a required quantity of biomass with enzyme activity of 900 000-1 000 000 U/L. Acrylonitrile is added at a slow rate to keep the acrylonitrile level below toxic levels and to avoid polymerisation. A reaction that takes place in the reactor is as follows:

(3) ##STR00001##

(4) In one example (as shown in the reaction above) the acrylic acid, produced during the biocatalyzed process of the invention, is combined with ammonia (NH.sub.3) which reacts in-situ with the acrylic acid (C.sub.3H.sub.4O.sub.2) to produce an ammonium acrylate (C.sub.3H.sub.7NO.sub.2) solution (with a pH between 6.8-7.1) which is a suitable precursor in the manufacture of certain polymers.

(5) The advantage of using ammonium acrylate produced from an acrylic acid obtained from the biocatalytic process herein described is that the acrylic acid is relatively free of undesired by-products, as the acrylonitrile substrate has been converted to acrylic acid in a single enzymatically catalysed step, without any unwanted side-reactions.