Use of Prosopis Africana Seed Hydrolysate as Peptone Source for Microbial Growth Media

Abstract

There is a growing industrial demand for peptones of non-animal origin owing to legislations as well as outbreak of animal-associated diseases. Microbiological growth media developed from legumes as sources of protein hydrolysates are limited. It is, therefore, the aim of this study, to produce comparatively standard protein hydrolysates from Prosopis africanaseed that can be used as peptone for microbial culture in place of animal peptone. Prosopis africana seeds (2.5kg) were purchased from a local market in Mbu-Akpoti, Enugu State of Nigeria. Stones and bad seeds were sorted out. The selected seeds were washed using distilled water and then boiled until the seed coats became soft. The softened seed coats were manually peeled off to reveal the cotyledons, which were collected, washed, dried and powdered. The powdered cotyledon was subjected to hydrolysis using the enzyme papain or hydrochloric acid. Metal ions, vitamins as well as proximate compositions of the hydrolysates were determined using standard methods. Amino acid analysis was done using HPLC. Growth patterns of Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, Candida albicans and Aspergillus niger were monitored in the media formulated using the seed hydrolysates. Peptone in commercially available MacConkey, Mannitol-salt and Sabouraud dextrose media was substituted with the seed hydrolysates and these were used as selective or differential media for specific organisms. In assessing the above parameters, comparism between commercially available peptone and the hydrolysates from Prosopis africana seed were made. The results of the analyses revealed that papain hydrolysed Prosopis africana seed (PHPs) ranked highest in terms of microbial growth support when compared to AHPs. PHPs and AHPs had moisture contents of 32.7and 83.3% respectively as against 3.93% in CP. The ash values were 3.05 and 0.15% for PHPs and AHPs respectively whereas CP had 4.08%. Crude proteins of 39.69 and 12.78% were also observed in PHPs and AHPs respectively. The hydrolysates were found to be rich in vitamins A, B, C and E and also in metal ions. Serine, threonine and lysine were the most dominant amino acids in the seed hydrolysates. Escherichia coli, Staphylococcus aureusand Candida albicans all thrived well in their respective selective media made with the hydrolysates, and this compared favourably well with commercially available peptone. Production and use of Prosopis africana seed hydrolysate as source of peptone will help to bring down the cost of peptones which are currently being imported and sold at very high rates in Nigeria.