This study aimed to characterise the production of lovastatin and its co-metabolites, sulochrin and (+)-geodin by A. terreus. Firstly, the study revealed that the types of carbon source influence lovastatin production, whilst the types of nitrogen source influence (+)-geodin and sulochrin production. Glycerol and yeast extract culture produced reasonable amount of lovastatin (25.68 mg/L), (+)-geodin (9.00 mg/L) and sulochrin (22.35 mg/L). This culture also produced pellets with hairy morphology, which is optimal for metabolite production.
Secondly, the potential of crude glycerol (CG) as the substrate for A. terreus cultivation was investigated. At 30 g/L CG, (+)-geodin (13.14 mg/L) and sulochrin (14.79 mg/L) increased ~2-fold, but lovastatin production decreased by ~35%. The presence of saturated fatty acids (~48% reduction) and soap (~90% reduction) contributed to the inhibitory effect of CG on lovastatin production, with no effects on (+)-geodin and sulochrin production. Partial purification of CG using solvent and activated carbon resulted in an improved yield of all three metabolites.
Thirdly, this study investigated the effects of selected ‘elicitors’ on the production of metabolites. Chemical elicitor was found to stimulate the production of lovastatin and sulochrin. (+)-geodin’s production was suppressed in high viscosity condition (<13 mg/L), whilst its production was stimulated by high shear force (>500 mg/L). These observations indicate that lovastatin and sulochrin may play a role in A. terreus’ defense mechanism. (+)-geodin, however, may be important for fungal pellet integrity or immediate response to injury, as physical elicition greatly enhanced its production.
In conclusion, CG is a promising alternative substrate for metabolite production by A. terreus. This study, however, demonstrates no apparent relationship between the production of lovastatin, (+)-geodin and sulochrin by A. terreus.