Sustainable cultivation via waste soybean extract for higher vaccenic acid production by purple non-sulfur bacteria

Abstract: The biomass production of Rhodovulum sulfidophilum HPB.6 was optimized via response surface methodology (RSM), and the optimal medium components such as waste soybean extract, yeast extract, and Mg²⁺ were determined using “one-single-factor-at-one-time” approach. RSM used a three-factor and central composite rotatable design consisting of 21 experimental runs conducted to optimize the final medium components. The optimized conditions were as follows: 2.723 g/L waste soybean extract, 3 g/L yeast extract, and 22 mg/L Mg²⁺. Under optimized conditions of Rhodovulum sulfidophilum HPB.6, the biomass production was 4.665 ± 0.326 g/L, which was 5.7-folds higher than that under non-optimized conditions. Besides that, the total lipid production was 5.7 times higher corresponding to the increase in biomass productivity. In addition, there was a change in total fatty acid composition with omega 7 and omega 9 which increased from 55.4 to 62.21 and from 3.4 to 9.41, respectively, while omega 6 decreased from 9.79 to 4.54 and omega 3 could not be detected. This exploration of waste soybean under optimized conditions would be a significant impact for the higher biomass production from Rhodovulum sulfidophilum HPB.6. Graphic abstract: [Figure not available: see fulltext.]