NUTRITIONAL AND ANTIMICROBIAL ENHANCEMENT OF OIL FROM CASTOR SEEDS (RICINUS COMMUNIS LINN) BY SOLID STATE FERMENTATION WITH PLEUROTUS OSTREATUS

Abstract

This research was centered on detoxification of castor seeds using Pleurotus ostreatus through solid state fermentation, thereby enhancing its safety, nutritional contents and antimicrobial properties. The proximate analysis, mineral composition, antinutrient and amino acid composition of the unfermented castor seeds (UCS), castor seeds fermented with Pleurotus ostreatus (CPF) and commercial fermented castor seeds (CSF) were determined using standard methods. Microorganisms associated with CSF were isolated using standard microbiological methods. The antimicrobial effects of the oil extracts on the test microorganisms were determined using agar well diffusion method. The histopathological and haematological effects of the oil extract and safety of the samples were determined using albino rats. Bacteria isolated were Bacillus spp., Lactobacillus spp., Micrococcus varians, Streptococcus thermophilus and Proteus vulgaris while fungi isolated were Aspergillus flavus and Penicillium digitatum. The unfermented castor seeds (UCS) had the highest composition of carbohydrate (61.04 %), total ash (6.02%), crude fat (6.65 %), and fibre (6.62 %). Castor seeds fermented with Pleurotus ostreatus (CPF) had the highest protein contents of 20.47 %, while the commercial fermented castor seeds (CSF) had the highest moisture contents of 17.29%. CPF had the highest magnesium content of 7.16 mg/100g. CSF had the highest zinc content of 0.69 mg/100g. UCS had the highest calcium content of 0.30 mg/100g. CPF had the lowest tannin concentration of 0.05 mg/g. CPF and CSF had the lowest concentration of phenol (0.12 mg/g). UCS had the lowest concentration of alkaloids (0.99 mg/g) while CPF had the highest concentration (7.40 mg/g). CPF had the lowest concentration of flavonoids (0.48 mg/g) while UCS had the highest concentration of 0.65 mg/g. CSF had the lowest concentration of saponin 1.40 mg/g while CPF had the highest concentration 6.69 mg/g. Glutamine and asparagine were absent in the unfermented and fermented castor seeds. Tryptophan was absent in the unfermented castor seeds (UCS) and had the lowest concentration in each fermented group: 0.78 mg/100g and 1.15 mg/100g for CSF and CPF respectively. Glutamic acid had the highest concentration in all the samples: 10.02 mg/100g, 0.22 mg/100g and 14.59 mg/100g for UCS, CSF and CPF respectively. Oil extract from CPF was able to inhibit the test microorganisms more than the other oil samples. The haematological analysis of the rats fed with UCS, CSF and CPF revealed that CPF had the highest WBC of 5.43×109. The histopathological analysis revealed that the organs of the rats fed with CSF had normal structure while the groups fed with UCS and CPF showed damages like dilation of sinusoids and degenerated hepatocytes in their liver while kidney showed shrunken glomerulus, haemorrhagic lesions etc. This study revealed that Pleurotus ostreatus enhanced the nutritional and antimicrobial properties of castor seeds. It also helped to degrade the toxic compounds in castor seeds to a large extent