Utilisation of orange peel in the production of α-terpineol by Penicillium digitatum (NRRL 1202)

The use of orange peel oil in the biotransformation of d-limonene was investigated. The physicochemical properties of cold-pressed orange peel oil, used in this investigation were determined to define its identity. The chemical composition of orange peel oil was determined by using GC/MS. Monoterpene compounds amounted to 98.0%, followed by aldehdyde components 1.09%. The main component of orange peel oil was d-limonene, which represented 96.1%, of the total content. A strain of Penicillium digitatum NRRL 1202 was used to carry out the biotransformation of d-limonene to α-terpineol. Two different media, malt yeast broth (MYB) and malt extract broth (MEB) were used. It was found that the highest bioconversion of d-limonene into α-terpineol was obtained by using MYB medium (pH 6.1). terpineol selectivity was recorded as 67.7%, by using MYB medium at 25–27 °C, 31 h after the second substrate addition. Meanwhile, the selectivity was 47.1% by using MEB medium (pH 5.4) under the same conditions. The bioconversion, in MYB medium, increased with increasing time, where it was recorded 79% and 95.5% 3 h and 7 h after the second substrate addition on the first day, respectively. Meanwhile, bioconversion of d-limonene on the second day reached 91.0% 7 h after the fourth addition of orange peel oil. By contrast, the bioconversion of d-limonene on using MEB medium was 87.8% 7 h after the second substrate addition on the first day. Meanwhile, bioconversion of d-limonene in the same media reached 100% 7 h after the fourth addition of orange peel oil on the second day.