Production of Microbial Milk Fats by Precision Fermentation

Abstract

Sustainable production of milk fats, specifically short-chain fatty acids (SCFAs), presents significant challenges for realizing cost-effective microbial milk production. This study investigates the optimal conditions required for SCFA production through microbial fermentation, focusing on the capabilities of selected commercial probiotics from the market related to genus Lactobacillus namely L. plantarum 23303, L. rhamnosus 6907 and 2 commercially available probiotics (BioFora and CP Probiotic). The research focuses on optimizing the fermentation of low-cost substrates, such as food waste.

MRS (De Man–Rogosa–Sharpe) and designed food waste collected, blended at a control moisture content and utilized as source of nutrients, inoculated with 5% v/v single strain in a 500ml shake flask experimental set up. pH optimization was conducted in a 2.5-liter Fermac bioreactor at a controlled temperature and agitation speed. The MRS media was utilized in preliminary studies to optimize temperature within the mesophilic range of 25℃ to 44℃. High Performance Liquid Chromatography (HPLC) was used to quantify SCFA production and glucose consumption. UV-VIS spectroscopy and dry cell weight (DCW) were used for growth.

Result showed that all strains effectively grow and metabolize optimally at 28℃ and pH 6.5 both in MRS and food waste. Acetic acid (AA) emerged as the primary SCFA produced, with trace amounts of propionic acid (PA) detected, butyric acid (BA) was not detected by the HPLC. The production rates of acetate were significantly higher at 28°C, with L. rhamnosus 23303 with acetic acid yield as high as 565.49 mg of SCFA/ g of glucose. Moreover, we observed that glucose conversion to SCFAs peaked at 72% for the BioFora strain at 28°C, compared to just 55% at 25°C. This clearly indicates that maintaining the right temperature can enhance metabolic pathways and boost SCFA production. The specific growth rates were also highest at 28°C, with BioFora and L. plantarum 23303 reaching about 0.061 h⁻¹ and 0.0715 h⁻¹, respectively. L. rhamnosus 6907, glucose consumption was most efficient at 28°C, where BioFora recorded a consumption rate of 0.091 g/g/h.

Date of Award	17 Dec 2024
Original language	American English
Supervisor	Srinivas Mettu (Supervisor)