Solid form of (−)-Ambrox formed by a bioconversion of homofarnesol in the presence of a biocatalyst

1. A method of preparing a solid form of (−)-Ambrox of the formula (I)

wherein, said solid form is characterized by at least one of the following characteristics:

it exhibits an x-ray diffraction pattern having at least one of the following peaks at diffraction angles 2 theta of 15.6, 16.2, 16.7, 17.0, 17.4, 18.3 +/−0.2°;

it comprises elongate crystals having an average diameter of at least 10 to 400 microns measured by laser granulometry;

it comprises elongate crystals having a length along their longest dimension of greater than 100 micron; and/or

it has an L* value of 90 or more; an a* value of less than 1 and greater the −1; and a b* value, which is less than 8, wherein L*, a* and b* values represent CIELAB L*a*b* chromaticity coordinates,

wherein the solid form of (−)-Ambrox is formed by a bioconversion process, said method comprising the steps of:

I) forming crystalline (−)-Ambrox in a bioconversion medium by means of a biocatalytic process; and

II) separating the crystalline (−)-Ambrox from the bioconversion medium.

2. The method according to claim 1 , wherein the separation step is a filtration step, a decantation step, or a combination of both a filtration step and a decantation step.

3. The method according to claim 1 , wherein prior to the separation step, the bioconversion medium is heated to a temperature of at least 80° C. to melt the crystalline (−)-Ambrox; and thereafter slowly cooled in order that the (−)-Ambrox is recrystallized from the bioconversion medium.

4. The method according to claim 1 , wherein the recovered crystals of (−)-Ambrox are solubilized in a solvent, and the solution filtered through a sub-micron filter to remove any residual particulate material that was present in the bioconversion medium, before being rendered in solid form by removing the solvent by evaporation or recrystallization.

5. The method according to claim 1 , wherein the bioconversion process is an enzyme-catalyzed cyclization of homofarnesol comprising a mixture of 7E,3E and 7E,3Z geometric isomers of homofarnesol, wherein the reaction is carried out in the presence of a biocatalyst, and wherein the biocatalyst is a recombinant microorganism expressing the gene coding the enzyme, or an isolated enzyme, or an immobilized enzyme.

6. The method according to claim 5 , wherein the enzyme is a wild-type squalene hopene cyclase, or a variant of the wild-type squalene hopene cyclase.

7. The method according to claim 1 , wherein the crystals are washed with water, water-miscible solvents or mixtures thereof.

8. The method according to claim 1 , wherein recovery of the (−)-Ambrox is achieved by its mechanical removal from a filter or decanter apparatus or belt filter, collection and drying.

9. The method according to claim 4 , wherein the solution of the solubilised (−)-Ambrox crystals is contacted with a bleaching agent.