Biotransformation of terpenic substrates by resting cells of Aspergillus niger and Pseudomonas putida isolates

Readily available and low cost terpenic compounds like (+) limonene, (-) limonene, (+) α-pinene, (-) α-pinene and (-) β-pinene, were used as substrates for biotransformation by a local fungal isolate of Aspergillus niger and a bacterial strain of Pseudomonas putida. The cultures were grown in potato dextrose broth at 30°C to their exponential phase and harvested. The resting cells were taken in phosphate buffer (0.05M; pH 7.0). Each substrate was added separately (2 mg/25 ml buffer) and incubated at 30°C for 6 h, after the reaction the flavouring compounds were extracted in dichloromethane, dried over anhydrous sodium sulphate, identified and analysed by GCMS. Aspergillus niger could use (-) limonene as the substrate to give carveol (18%) and dihydrocarveol (15%). Bioconversion from (+) α-pinene was better with Pseudomonas putida, producing industrially important compounds like verbenol (35%), dihydrocarveol acetate (20%) and verbenone (10%) in high yields. However, the bacteria was unable to bioconvert (-) α-pinene, (-) β-pinene, and (-) (+) limonenes to these important compounds.