Optimization of Fermentation Conditions for Protein Production from Prosopis africana Seeds using Response Surface Methodology

Abstract

Due to the rising protein malnutrition because of high cost of animal protein in many countries in Africa including Nigeria, this renews the interest in legume seeds as potential sources of vegetable protein for human food. Prosopis africana seeds is one of the under used leguminous seeds crops added to food as a condiment called Okpehe. This study was designed to establish optimum conditions for the fermentation of Prosopis  africana seeds into vegetable protein based condiment (Okpehe) using Response Surface Methodology (RSM) with four (4) variables namely; fermentation duration (X1), inoculums concentration (X2), pH (X3) and temperature (X4). Prosopis africana seeds were fermented at various temperatures of 35°С, 40°С, 45°С and 50°С for four days (96 hours).The inoculums used for fermentation contained (7.5×10⁸ cells/5ml^-1 , 1.5×10⁹ cells/10ml^-1 and 2.3×10⁹ cells/15ml^-1 into 20g of boil unfermented P. africana seeds. The cell population was calibrated using McFarland standards (No1). The interaction effects of these four variables on the % protein yield were investigated using Central Composite Design (CCD) fractional design of experiments. From experimental data generated by the design of experiment (DOE), using MINITAB 17 software, optimum conditions were obtained at 40⁰C, with inoculum (Bacillus licheniformis) concentration of 1.5×10⁹ cells/10ml^-1 with pH 7 at fermentation duration of 96 hours. The adequacy (R²) of the models was highly satisfactory for the processes being 0.90. In conclusion, it was observed that protein content of fermented Prosopis africana seeds were increased during fermentation because, Protein had the highest yield of  44.52 % after 96 hours of fermentation at temperature of 40°С.

Key Words: Prosopis africana, fermentation duration, Okpehe and Response Surface Method