Optimization of Lactic Acid Fermentation from Durian Seeds (Durio zibethinus Murr.) Using Response Surface Method

Abstract

Lactic acid production in Indonesia has not been able to meet the needs of the industry, especially as the raw material for biodegradable plastic/poly lactic acid (PLA), thus an inexpensive and abundant alternative material is needed, based on previous research, durian seed waste has the potential as a raw material to produce lactic acid by fermentation using Lactobacillus Plantarum bacteria, but there is no optimization yet. This study aimed to determine the optimization mathematical modeling of the variables that affected yield and concentration of lactic acid, namely substrate concentration (15%), inoculum concentration (2%), and yeast extract concentration (10 g/L), using the Response Surface Method (RSM) and Central Composite Design (CCD) to save time and costs. This research was conducted in several stages, preparation of raw materials, testing the proximate value of the materials, inoculation and rejuvenation of bacteria, fermentation at 37°C, agitation speed of 100 rpm for 72 hours, then the fermentation results were analyzed using UPLC (Ultra Performance Liquid Chromatography) for its lactic acid concentration. Response Surface Method (RSM) was executed by using software Minitab 17. The obtained mathematical equation model for the fermentation reaction of lactic acid production was Y = 22.49 + 1.883X1 + 1.305X2 + 1.380X3 - 3.273X1*X1 - 2.558X2*X2 - 1.475X3*X3 - 0.968X1*X2 + 0.390X1*X3 + 0.954X2*X3 with the optimum conditions for substrate concentration, inoculum concentration, and yeast extract concentration respectively of 15.14%, 2.16% and 10.3 g/L.