Volume 10 Part 1 Article 37: Lipid Metabolism of Mushroom Mycelia

Volume 10 Part 1 Article 37
Year 1979
Title: Lipid Metabolism of Mushroom Mycelia
Authors: R.B. Holtz and D.S. Smith

Abstract:

The mycelia-compost interface is a key area of concern in the overall understanding of the nutrition of Agaricus bisporus. This interface and its biochemical activities are the primary regulators of nutritional events since transport of material into and out of the cell is executed.

Lipid metabolism has long been a key area of interest in the nutrition of the commercial mushroom. Early experiments have described the stimulation of yield with polyunsaturated fats and oils (Schisler, 1962, 1967, 1970).

Holtz and Schisler (1972) studied in vivo sporophore lipid biosynthesis of A. bisporus. Using uniformly labeled 14C-linoleic acid and 14C-acetate as added supplements to mushroom compost, it was found that 14C incorporation from both substrates followed similar patterns. Fatty acids were labeled proportionally to their mass. However, free sterol was labeled in a greater proportion than its mass. From the labeling data it was suggested that the most probable way for labeled carbon in linoleic acid to be incorporated into sterol was via B-oxidation to acetate and subsequent synthesis via the mevalonate pathway.

Isolation of cellular components revealed that the primary location of free sterol in A. bisporus is in the plasma membrane (HOLTZ et al., 1972).

Vegetable oil supplements are primarily triglyceride when added to compost. Triglycerides are not easily transported across the plasma membrane. Transport more readily occurs as the free fatty acid or a smaller oxidation intermediate. Therefore, the initial nutritional event in the utilization of vegetable oil supplements in the compost is the action of a triglyceride lipase. The research reported below was initiated to more fully describe this area of nutrition in A. bisporus. The general characteristics of mycelial lipases were investigated. Also, biochemical indicators of metabolic activity were monitored.

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