Castor seed is important because of the castor oil content (40 – 57%). The oil enjoys tremendous world demand in the pharmaceutical, paint, cosmetics, textile, leather, lubricant, chemical, plastic, fibre, automobile and engineering industries. Castor oil, aside being a renewable resource, it is biodegradable and eco-friendly. Agricultural products are natural habitats of fungi and these materials contain cellulose, hemi-cellulose, starch, oils and other complex organic compounds. The ability of the fungi to exist in these environments largely depends on their ability to produce enzymes capable of breaking down the various organic materials to provide their nutrients. Castor seeds and castor oil are good sources of nutrients for fungal growth and development. Fungi are capable of producing lipases which can hydrolyze fats or oils to fatty acids thereby increasing the free fatty acids of the produce and this is a deteriorating effect. Lipid degradation takes place when seeds or their oils are damaged by improper storage conditions or are exposed to certain microorganisms. Studies were carried out on the ability of nine fungal species namely:
Aspergillus tamarii
Aspergillus chevallieri
,
Penicillium chrysogenum
,
Cephaliophora irregularis
,
Syncephalastrum racemosum
,
Aspergillus flavus
,
Aspergillus ruber
,
Aspergillus terreus
and
Aspergillus niger
to produce extracellular lipases in stationary liquid medium using quantitative and qualitative indices including, dry mycelia mass, free fatty acid and peroxide values. These studies showed that all the mould species exhibited lipolytic activity to varying levels as confirmed by formation of blue halo round the fungal colonies. The highest level of lipolytic activity (96.88% ± 1.12%) was produced by
Aspergillus tamari. which was also characterized by highest mycelia dry yield (2.54 mg/40ml ± 0.20 mg/40ml), while
Cephaliphora irregularis produced the least lipolytic activity (3.10 % ± 0.18%). The highest peroxide value (38.1 meq/kg ± 1.17meq/kg) was obtained in the medium inoculated with
Aspergillus tamarii while the least (6.20 meq/kg ± 0.58)meq/kg was with
Aspergillus terreus after 30 days of storage. The study showed that
Aspergillus tamarii and
Aspergillus flavus grew well and readily caused lipolytic activity when cultured in medium containing castor oil as the only carbon source, suggesting that these fungal species contributed significantly to castor oil bio-deterioration.