IMPROVEMENT OF BIOSURFACTANT PRODUCTION BY BACILLUS SP. KG7’B THROUGH BIOPROCESS ENGINEERING AT THE LABORATORY SCALE

• Main Author: Rahmatunisa, Nadira
• Format: Theses
• Language: Indonesia
• Subjects: Teknologi
• Online Access: https://digilib.itb.ac.id/gdl/view/80484
• Institution: Institut Teknologi Bandung

Biosurfactant is amphipathic compound produced by microorganisms that can be used in a variety of industries. Biosurfactant is biodegradable and has lower toxicity than synthetic surfactant, thus make biosurfactant more eco-sustainable. However, industrial-scale production of biosurfactants is hampered by low productivity, finding it challenging to satisfy market demands. Previously, an approach to enhance biosurfactant production by wildtype (WT) Bacillus sp. had already focused on metabolic engineering through adaptation laboratory evolution (ALE). Stable mutant with high emulsification activity but low production capability (0.27 ± 0.05 g/L) were obtained from this process. As a result, bioprocess engineering was carried out in this study by modifying the substrate concentration to increase the biosurfactants production. The increment in biosurfactant production was reached by using an optimization approach to fermentation conditions, specifically the ratio of carbon and nitrogen sources (C/N) in the medium, and even by optimizing the age of the inoculum using response surface methodology (RSM). The optimization parameters were evaluated based on the response to the biosurfactant production kinetics in the form of:(1) biosurfactant productivity, (2) production yield (Yp/x), and (3) concentration of biosurfactant obtained. The study also investigated the structure and the stability of biosurfactants under various environmental conditions such as temperature, pH, and salinity. The results of the analysis revealed that n-hexane is an alternative carbon source which Bacillus sp. KG7'b can use it to produce biosurfactants. The optimum biosurfactant productivity was 18 mg/L.hour using medium with a C/N ratio of 5.1 and an inoculum age of 14 hours. At a C/N ratio of 7.6 and an inoculum age of 18 hours, the optimal Yp/x value of biosurfactant was 24.8 ng.mL/CFU. The optimum concentration of biosurfactant was achieved using a C/N ratio of 3.8 and an inoculum age of 12 hours, resulting in a biosurfactant concentration of 0.68 ± 0.02 g/L, or equivalent to a 2.5-fold increase in production compared to prior metabolic engineering results. The results of the biosurfactant stability study on environmental variations in temperature, pH, and salinity upon its assessment of emulsification index (%E24) in heavy crude oil (ABG3), light crude oil (CEPU), and cooking oil (BML) revealed that the biosurfactant obtained was stable at a temperature range of 20 – 100 oC and pH 2 - 12 but not stable when more than 2% (w/v NaCl) salinity was added. Fourier-transform infrared spectroscopy (FTIR) analysis of the biosurfactant's structure revealed that it belongs to the non-surfactin lipopeptide class, which is dominated by hydrophilic groups and seems to be susceptible to interaction with Na+ ions. The structure of the biosurfactant produced distinguishes it from the biosurfactant produced by WT prior to the ALE process as well as the biosurfactant produced by KG7' even before the optimization process.