Citric acid production by Yarrowia lipolytica from crude glycerol: Influence of oxygen mass transfer rate (OTR)

摘要

Glycerol from biodiesel industry, which is available in high amountsnowadays, is a renewable low-cost substrate that can be used formany biotechnological applications. Yarrowia lipolytica is a strictlyaerobic yeast, known for the ability to use several carbon sourcesand to produce several high value compounds. Citric acid, an intermediateof tricarboxylic acids cycle, is extensively used in foodand pharmaceutical industry. This organic acid can be producedby Y. lipolytica from glycerol under specific growth conditions,namely under nitrogen limitation. Oxygen availability in the culturemedium is also an important factor that influences these aerobicbioprocesses.In this work, the influence of Oxygen Transfer Rate (OTR) fromair to the culture on citric acid production by Y. lipolytica W29(ATCC 20460:CLIB89) using crude glycerol was evaluated. Batchcultures with 50 g L1 of glycerol were performed at OTR valuesfrom 52mgL1 h1 to 878mgL1 h1 obtained varying aerationand agitation rates, from 1vvm to 3 vvm, and from 200rpm to600 rpm, respectively.The increase of OTR up to 408mgL1 h1 leaded to a 7.7-foldincrease of citric acid production (10.8±0.5gL1). Further increaseof OTR values above 408mgL1 h1 did not improve citric acid concentrationand productivity. In fact, for these OTR values oxygendissolved concentration in the medium was kept above 50% of thesaturation value, during the production of citric acid, meaning thatthe process control by oxygen limitation was prevented.