Springer Online Journal Archives 1860-2000
Process Engineering, Biotechnology, Nutrition Technology
Abstract A citric-acid-producing Aspergillus niger strain was cultivated in conditions favouring citric acid biosynthesis and in conditions hindering it. During both extreme processes, the mycelia were analysed for their lipid content, individual lipid classes, the content of sterols and free fatty acids. Since phospholipids, especially phosphatidylcholine and sterols, play an essential role in membrane permeability one can conclude that the differences observed substantially contribute to citric acid excretion into fermentation media. The difference in sterol composition was the most pronounced. Citric-acid-excreting mycelia contained lower quantities of sterols and ergosterol was the only component. A. niger mycelia grown in conditions hindering citric acid accumulation contained higher amounts of sterols with ergosterol as the main component and six other sterol components representing a minor amount.
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