John A. Alford

Production of microbial lipases for the study of triglyceride structure

Lipases from different microorganisms are known to differ in their site of attack on triglycerides, and recent evidence has indicated that they may be useful in studying triglyceride structure. This paper is concerned with the most recent developments in the production, recovery, and stability of lipases from three of these microorganisms. The lipase fromStaphylococcus aureus, which attacks both the 1-, 2-, and 3-positions of triglycerides, is produced in an aerated, tryptic digest of casein at 30C in 1–2 days. The lipase fromGeotrichum candidum, which attacks primarily unsaturated fatty acid linkages and shows some stereospecificity, is produced in a static culture grown on a mineral salts-glucoseprotein hydrolysate medium incubated at 20C for 4–5 days. An improved method is described for preparing lyophilized preparations of these, and thePseudomonas fragi lipase, which are quite stable when stored in a refrigerator.

Specificity of a lipase fromGeotrichum candidum forcis-octadecenoic acid

A lipase fromGeotrichum candidum released mostly oleic acid from glyceryl 1-elaidate-2,3-dioleate and very littletrans fatty acid from margarine. When cod liver, Macadamia nut, peanut and safflower oils were substrates, the oleic acid content of the free acids was always in excess of the amount of the acid in the intact triglycerides. Congo palm oil was digested by bothG. candidum and pancreatic lipases and the fatty acid compositions of the products of hydrolysis compared. The results obtained with the aid ofG. candidum lipase tend to substantiate existence of some of the triglyceride isomers predicted from pancreatic lipase data.

Presence of antioxidant materials in bacteria

Fourteen species of gram-positive and gram-negative bacteria from nine genera were investigated to determine if they produced compounds that have antioxidant activity. Washed bacterial cells were extracted with methanol for 24 hr. This extract was evaporated to dryness and extracted with benzene. The fractions were added to lard and incubated at 58 C. Antioxidant activity was determined by prolongation of the period required for the initiation of rancidity as measured by changes in peroxide value. The methanol soluble-benzene soluble fractions ofBacillus cereus, Lactobacillus dextranicum, Micrococcus freudenreichii andSarcina lutea showed considerable antioxidant activity. Methanol fractions of threePseudomonas species showed considerable activity that could not be extracted with benzene. The possibilities of using microbial growth on fats as well as extracts of microorganisms added to fats as antioxidants are discussed.