Statistical Optimisation of Fermentation Conditions for Citric Acid Production from Pineapple Peels.

Abstract

This study investigated the optimisation of fermentation conditions during citric acid production via solid state fermentation (SSF) of pineapple peels using Aspergillus niger. A three-variable, three-level Box-Behnken design (BBD) comprising 17 experimental runs was used to develop a statistical model for the fermentation process while response surface methodology (RSM) was used for the optimisation of fermentation conditions. Increasing the fermentation temperature and the moisture content of the solid substrate enhanced the production of citric acid. Increasing the broth pH did not favour citric acid production as higher citric acid concentrations were recorded at low pH values. These results showed that citric acid production was influenced by these variables (i.e. temperature, moisture content and pH). The optimal fermentation conditions were determined as follows: fermentation temperature, 35 o C; broth pH, 2 and initial moisture content, 84.56%. The maximum concentration of citric acid produced under these conditions was 72.41 g/l. These results imply that the metabolic activity of the fermenting organismn (Aspergillus niger) used in this study was maximum at these optimised conditions. Validation of the statistical model indicated no difference between predicted and observed values as seen in the high correlation between model predicted results and experimental results.

Application of Experimental Design Method for the Optimisation of Xanthan Gum Production from Pineapple Peels Using Xanthomonas Campestris via Submerged Fermentation

“…The experimental design was developed using Design Expert ® 7.0.0 (Statease, Inc. Minneapolis, USA). The coded and actual values of the independent variables were calculated using Equation (2).…”

“…Under these conditions, the xanthan concentration was concentration were 3 days, 2 g/L and 15 g/L respectively. Under these conditions, the xanthan concentration was obtained as 8 [1].The processing of pineapple into different fruit drinks and other products typically results in the generation of solid pineapple wastes particularly the peels which account for about 10% of the weight of the original fruit [2]. These wastes are typically disposed of improperly particularly in less developed countries thereby causing serious environmental pollution problems.…”

Determination of Optimum Composition of Fermentation Medium for Citric Acid Production from Watermelon Rinds using Response Surface Methodology

“…The dried peels were then milled using a laboratory hammer mill and then sieved to obtain 2 mm particles. 7 spores/mL [10] . [11] .…”

“…It has a higher citric acid yield, lower energy and water requirements, less risk of bacterial contamination, less wastewater generation and less environmental concern regarding the disposal of solid waste [8] . Several researchers have investigated SSF as a route to producing citric acid from abundantly available solid waste materials such as sugarcane bagasse [9] , pineapple peels [10,11] , apple pomace [12] , banana peels [13,14] , date palm [15] , carob pod [16] , and grape pomace [17] . Watermelon rind is basically the left-over after the consumption of the juicy part of the watermelon pod.…”

“…Optimisation of fermentation nutrient medium by the traditional one-factor-at-a-time method is often cumbersome and time-consuming. Response surface methodology (RSM) has been found to be very useful in optimising multivariable processes and it has been successfully applied to the optimisation of citric acid production from other agricultural residues [2,4,6,10,11] . The objective of this study was to optimise the nutrient medium for the production of citric acid from watermelon rind via solid state fermentation using Aspergillus niger.…”