Antifungal peptides have been successfully extracted from whole body larvae of Zophobas morio (Fabricius) by using acidified isopropanol. To ensure that the extraction is cost effective for maximum yield, Response Surface Methodology (RSM) using a Central Composite Design (CCD) strategy was adopted to optimize the extraction process parameters. The effect of independent parameters, namely, the homogenization temperature (°C), homogenization time (min) and solid (g) to the solvent (ml) ratio of the extraction process on the fungal growth was studied. The extracted samples obtained by conducting runs accorded by the experimental design showed varying degree of antifungal activity against Aspergillus niger, the selected fungal strain, as assayed by the ‘‘Poisoned agar technique’. The investigation showed that the optimum values of the extraction parameters for the maximum antifungal peptides were 5 minutes homogenization time, 4°C homogenization temperature and 3.5:1 solid to solvent ratio. This study reports the development of an extraction process that allows careful recovery of antifungal peptides from larvae. In the validation of the experimental model, the error between the actual value and the predicted value was determined to be 3.57%.
Acidified isopropanol extract of whole body larvae of Zophobas morio (Fabricius), which contains peptides, has been shown to exhibit an inhibitory effect towards fungal growth. The larvae, commonly known as supermeal worm are cheap and easily maintained. To make the extraction even more cost effective, it is pertinent to maximize the extraction yield and to optimize the extraction process. The aim of this study is to use the One-Factor-At-a-Time (OFAT) strategy to determine the maximum values of the process parameters for the extraction of antifungal peptides, where these values can later be used in the experimental design to optimize the extraction process. Based on importance, three parameters were selected, namely, initial homogenization temperature, homogenization time and solid (g) to solvent (ml) ratio. Maximum inhibition to fungal growth was found when the extraction was carried out as follows; using initial homogenization temperature of 4°C, homogenization time of 5 minutes and a solid (g) to solvent (ml) ratio of 3.5:1. The peptide extract displayed different degree of antifungal effect towards four selected fungi, Aspergillus niger, Microsporum canis, Candida albicans and Blastomyces dermatitidsis.