it is to be understood by a person having ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention . the following example is provided to further illustrate the invention and is not to be construed to unduly limit the scope of the invention . for a better understanding of the invention , and to show how embodiments of the same may be carried into effect , reference will now be made , by way of example , to the following figures and examples in which :— fig1 shows the conversion of different concentrations of 2 - butanone by 5 μm chmo . all chemicals were of analytical grade and obtained from sigma aldrich . cyclohexanone monoxygenase from acinetobacter ncimb 9871 ( chmo , ec 1 . 14 . 13 . 22 ) was expressed and purified fused to the n - terminus of a thermostable phosphite dehydrogenase ( ptdh , ec 1 . 20 . 1 . 1 ) for cofactor regeneration , as described above . transformations were performed in 15 ml pyrex tubes . reaction volumes ( 1 ml ) contained 5 mm 2 - butanone , 100 um nadph , 10 mm na 2 hpo 3 and 5 μm chmo in 50 mm tris - hcl , ph 7 . 5 . mixtures were incubated at 24 ° c . under orbital shaking ( 200 rpm ). to determine conversion , 1 ml reaction volume was extracted with 0 . 5 nil 1 - octanol containing 0 . 1 % mesitylene ( 1 , 3 , 5 - trimethylbenzene ) as internal standard . samples were extracted by vortexing for 1 min , followed by a centrifugation step ( 5000 rpm ) for 10 min . the organic layer was removed , dried with mgso 4 and placed in a gas chromatography ( gc ) vial . gc analysis occurred on a shimadzu gc instrument fitted with a heliflex ® at ™- 5 column ( grace discovery sciences ). the following temperature profile was used to separate the components : 6 min at 40 ° c . followed by an increase to 250 ° c . at 20 ° c . per minute . blank reactions without enzyme and with varying amounts of substrate ( 2 - butanone ) and product ( methyl propionate , ethyl acetate ) were carried out under identical circumstances and used to prepare calibration curves for product identification and determination of conversion . table 1 below details the separation time of the compounds by gc following extraction with 1 - octanol + 0 . 1 % mesitylene from 50 mm tris - hcl , ph 7 . 5 ( at - 5 column , 5 mm all compounds ). all three compounds ( 1 substrate and 2 products ) could reliably be separated by gc . table 2 below details the conversion of 2 - butanone to ethyl acetate and methyl propionate by chmo . co - factor regeneration was carried out by the chmo fusion partner ptdh ( 1 ). clearly , an industrially significant amount of methyl propionate is formed after 24 hours . further bvmo enzymes were also tested for the conversion of 2 - butanone to methyl propionate using the method stated above for chmo in table 2 . table 3 shows the results of screening ten bvmo enzymes a - j including chmo . an industrially significant amount of methyl propionate is formed after 20 hours for the bvmo enzymes , cpdmo and hapmo . fig1 shows that higher substrate concentrations yield more of the desired , abnormal product . for example : incubation with 5 mm 2 - butanone yields an ethyl acetate : methyl propionate ratio of 5 : 1 , and incubation with 1000 mm 2 - butanone yields a ratio of 1 . 5 : 1 various co - solvents were tested for their influence on the ratio of products formed in the reaction of acinetobacter sp . dsm 17874 chmo with 2 - butanone . as in the previous example , 200 mm 2 - butanone was observed to have a positive effect on this ratio . in particular , increasing the concentration of 2 - butanone results in the formation of more methyl propionate , improving the ethyl acetate : methyl propionate ratio . a number of co - solvents at this concentration ( 200 mm ) were tested . as can be seen from table 4 , 200 mm methanol has a dramatic effect , inverting the ratio completely in favour of methyl propionate . under these conditions , more methyl propionate is formed than ethyl acetate . the other co - solvents tested also showed a positive effect . dioxane , 2 - butanol , acetone and acetonitrile all had a significant positive effect on the ratio . the effect of co - solvents on the total amount of conversion was also studied , and is highlighted in table 5 . in some cases ( dioxane , acetone & amp ; acetonitrile ) significantly more methyl propionate is formed while less ethyl acetate is formed . to account for the different extraction efficiency of the substrates and products in the presence of co - solvent , here the calibrations were re - performed with co - solvent to rule out any significant differences . purification of a novel set of bvmos & amp ; screening them for the conversion of 2 - butanone the over - expression and purification of several different bvmos has been achieved , and is summarized in table 6 . the genes were all cloned into the pcre3c phosphite dehydrogenase fusion vector and expressed in e . coli top10 . by limiting the culturing temperature to 17 ° c . significant soluble over - expression was obtained for rmchmo and xfchmo . significant soluble expression was obtained for bpchmo . the purification protocol involved preparing cell free extracts by sonication in 10 mm sodium phosphate buffer ( ph 7 . 4 ) with the following additives : 10 % glycerol , 0 . 5 mm dithiothreitol , 100 mm nacl and 25 mm imidazole . the cell extracts were clarified by centrifugation and incubated with ni 2 + - sepharose resin for 2 hrs at 4 ° c . column material was washed with the same buffer after which the pure protein was eluted as a concentrated yellow fraction ( or as a pale band in the case of enriched enzymes ) and desalted by gel filtration . reassuringly , all chmos that were purified displayed similar activity towards 2 - butanone , converting it into methyl propionate and ethyl propionate , and all purified chmos had the same feature that when the concentration of 2 - butanone was increased the ratio of the products formed shifted in favour of methyl propionate . the different chmos have similar conversion amounts for methyl propionate , but the ratios of products formed are not identical . as will be appreciated , some examples show the use of different bvmo enzymes to produce methyl propionate or ethyl acetate . in these examples , particular bvmo enzymes are advantageously shown to produce methyl propionate in favour of ethyl acetate . however , some of the bvmo enzymes tested show no conversion at all , or only conversion to ethyl acetate . advantageously , the inventors have also discovered the bvmo enzymes which are surprisingly active in the abnormal conversion . in this preferred feature of the invention , the bvmo enzymes that do not show conversion to methyl propionate may be described as comparative examples i . e . examples a , b , d , e and h - j . attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification , and the contents of all such papers and documents are incorporated herein by reference . all of the features disclosed in this specification ( including any accompanying claims , abstract and drawings ), and / or all of the steps of any method or process so disclosed , may be combined in any combination , except combinations where at least some of such features and / or steps are mutually exclusive . each feature disclosed in this specification ( including any accompanying claims , abstract and drawings ) may be replaced by alternative features serving the same , equivalent or similar purpose , unless expressly stated otherwise . thus , unless expressly stated otherwise , each feature disclosed is one example only of a generic series of equivalent or similar features . the invention is not restricted to the details of the foregoing embodiment ( s ). the invention extends to any novel one , or any novel combination , of the features disclosed in this specification ( including any accompanying claims , abstract and drawings ), or to any novel one , or any novel combination , of the steps of any method or process so disclosed .