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Effect of ammonium-N on malic enzyme and lipid production in Rhodotorula glutinis grown on monosodium glutamate wastewater

Abstract Rhodotorula glutinis, an oil producing strain, can utilize monosodium glutamate (MSG) wastewater as a raw material for lipid production. The effects of ammonium-N in the MSG wastewater (ammonium 15,000–25,000 mg/L, COD 30,000–50,000 mg/L) on cell growth, lipid accumulation and malic enzyme activity of R. glutinis have been studied. Four initial ammonium sulfate concentrations in the medium were set, which were 20, 60, 100, and 140 g/L. With an increase in the ammonium sulfate concentration, the uptake of ammonia nitrogen and lipid accumulation increased while the biomass decreased at 72 h. The maximum value of ammonia nitrogen consumption reached 5.77 g/L for an initial ammonium sulfate concentration of 140 g/L at 72 h. In addition, 60 g/L ammonium sulfate concentration may be an appropriate concentration for R. glutinis cultivation. The activity of the malic enzyme was measured and the results showed that there was a linear relationship between the intracellular lipid content and the total malic enzyme activity.