The beta-galactosidase-based assay for lysine developed by Tuffnell & Payne was used to measure the bioavailabilities of cyst(e)ine, methionine, threonine and tryptophan in pronase digests of 17 foods. The digests were assayed by estimating the beta-galactosidase synthesis responses of five Escherichia coli mutants, each requiring one of the respective amino acids for protein synthesis. Deletion mutants were used whenever possible in order to ensure strain stability. Single digests of each food were assayed with 3 or 4 separate cultures of each mutant and the results were compared with those from the corresponding chemical assay. Omitting the anomalously low values for one food, the rank correlation coefficients of the bio- and chemo-assay values were 0.61 (cysteine), 0.91 (lysine), 0.95 (methionine), 0.64 (threonine) and 0.85 (tryptophan). Mean (+/- S.D.) relative amino acid bioavailabilities (casein = 100%) for the 17 foods were: cysteine, 53 +/- 23; lysine, 90 +/- 10; methionine, 95 +/- 18; threonine, 89 +/- 13; and tryptophan, 89 +/- 25. The cysteine mutant appeared to give unusually low bioavailability values except for the milk products. These amino acid mutants afford a rapid method for assaying the bioavailabilities of at least four of the five amino acids studied.

Summary Fat‐soluble fatty acid monoesters of 1‐ascorbic acid (vitamin C) and d‐isoascorbic acid have been prepared from lauric, myristic, palmitic, and stearic acids in 40–50 per cent yields. Evidence has been presented to show that only the primary hydroxyl group of each of the ascorbic acids has been esterified. Antioxidant properties of these esters are being studied. Preliminary tests on the esters have indicated that they may have useful properties as interfacial modifiers.

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The submerged cultivation of Rhizopus oryzae in rotary aluminum fermenters under stated conditions results in the fermentation of 13 per cent glucose solutions in 30 to 35 hours, with 70 to 75 per cent yields of dextrolactic acid. A carbon balance shows that, in addition to lactic acid and alcohol, an unidentified soluble material is produced equivalent to 7.4 per cent of the glucose consumed. Possible industrial advantages of this process are discussed.HE production of dextrolactic acid [also known as sarcolactic acid or I(+)lactic acid] by Rhizopus oryzm when cultivated on the surface of glucose nutrient solutions was the subject of previous communications from this division (6, 9). Surface cultivation gave 65 to 67 per cent yields of lactic acid in an incubation period of approximately 2 weeks. The present paper describes a process which involves the cultivation of this fungus in a submerged condition, whereby 13 per cent glucose solutions are fermented in 30 to 35 hours, with 70 to 75 per cent yields of d-lactic acid. This work is dependent on the use of the previously described rotary aluminum fermenters (4) which have also been employed as culture vessels to bring about the extremely rapid conversion of glucose to gluconic acid, using the organism Aspergillus niger (6, l l ) , and of sorbitol to sorbose, using the organism Acetobacter suboxydans (12). Materials and Methods TThe organism used in these studies was the previously described strain of Rhizopus oryzue Went and Geerligs (6), which was one of the best d-lactic said producers observed in the surface-growth studies. Although it is usually cultured on the surface of unagitated aedia, its growth and biochemical activity are enharxed when it is cultivated submerged under the favorable conditions described below.The culture of the organism in this work proceeded through the following three stages: (a) production ol' spores by growing on moist white bread for about 2 weeks, (b) germination of the spores in a glass bottle shaken during a period of 24 hours, and (c) the main fermentation, conducted in the rotary aluminum fermenters.The moist white bread cultures (one-half slice of bread in 200-cc. Erlenmeyer flasks) were inoculated from agar slants or from other bread cultures. After 5 to 6 days sporulation was profuse, and a t the age of about 2 weeks a portion of these spores was aseptically transferred to 50-75 cc. of sterile water and shaken to form a suspension, and a sample was removed to determine the spore concentration by means of a cytometer. A volume containing 420 million spores was then uised to inoculate 1.5 liters of germination medium. Usually this number of spores could be obtained from 5 to 10 cc. of spore suspension, and one bread culture would yield 5 to 10 billion spores.The germination medium had the following composition, in grams: Commercial glucose 110 KHzPO4 0.60 Urea 2 . 0 ZnSOa.7HzO 0.088 MgSO4.7HzO 0 . 2 5 CaCOa 10.0 Distilled water t o make 1000 oc.All of these components were sterilized together. The glucose was a commercial g...