Protein made on agave juice base
Chemical Congress-Mexico Waste agave juice can be used to pro duce single-cell protein of good nutri tional value, says Dr. A. SanchezMarroquin of Patronato de Maguey in Mexico City. The technique consists of growing a mixed culture of yeasts on low-sugar (2.5 to 5%) or spent agave juice, the researcher told a symposium on single-cell proteins. The product obtained with the tech nique contained 50% protein and a good nutritional balance of several crit ical amino acids. It also was rich in Β vitamins. The product thus compares well as a food protein with egg and soy beans, Sanchez-Marroquin says. And it thus offers good possibilities for use in human diets and feed supplements, he adds. Agave is one of the few plants capa ble of growing in the semiarid zone of Mexico because of its remarkable water-storing capacity. The juice ob tained after cutting the floral stem is fermented to form a popular Mexican drink called pulque, when the sugar content of the juice is about 10%. Sanchez-Marroquin and coworkers used the yeast culture technique to produce protein in a semi-industrial plant in a small town in the state of Hidalgo. The product was odorless, white, "very palatable," and readily soluble in water. He says the product showed no apparent toxicity in com monly used tests or when fed to tur keys during a short study. He estimates the cost of production as an animal feed at 5 to 8 cents per lb, and as a more highly refined human food supplement at 10 to 15 cents per lb. "The present estimates indicate that the cost of single-cell protein will have to compete with peanut butter and cottonseed and soy flours at prices from 10 to 12 cents a lb," he says. The technique to obtain protein from spent agave juice has several advan tages, according to Sanchez-Marro quin. These include efficient growth rate of the yeast; ease of recovery of protein; high protein content of the product; acceptable lysine, threonine, and tryptophan balance; good biologi cal value with 0.2% methionine added; and a high digestibility coefficient. The protein production method also is ap plicable to blackstrap molasses and in expensive sugarcane juice, the price of which is independent of the interna tional sugar market, the researcher says. "The advantages of single-cell pro tein production," Sanchez-Marroquin says, "are its higher nutritional value compared to vegetable protein; the 22
C&EN Dec. 15, 1975
process requires much less time to dou ble the mass of product than is needed by animal and vegetable proteins; the production of single-cell protein is not inhibited by climatic conditions that would limit or prevent the raising of agricultural protein in many parts of
the world; and finally, the total land area needed for production of singlecell protein is much less than for ani mal or vegetable farming. This is most advantageous in the overpopulated areas of the world, where availability of land for agriculture is low." G
Science
Tropospheric hydroxyl radical measured
Chemical Congress-Mexico Using laser-induced fluorescence, Uni versity of Maryland scientists have made the first measurements of the absolute concentrations of hydroxyl radical in the upper troposphere. The numbers, they say, show that the best models being used by scientists for cal culating concentrations are not very far off. The measurements were completed in late October at two sites, just in time to be presented at a general session on the environment. The measurements were made, in cooperation with the National Center for Atmospheric Research, in the El Paso area and in the Tampico-Vera Cruz area over the Gulf of Mexico. Pre liminary results: • Measurements taken Oct. 15 be
tween noon and 2 PM at 32° north lati tude and 106° longitude and at an altitude of 7 km showed hydroxyl radical concentration of 1 to 3 Χ 106 molecules percc. • Measurements on Oct. 24 between 12:20 PM and 2:00 PM at 21° north latitude and 96° longitude at an altitude of 7 km showed a concentration of 4 to 10 x 106 molecules per cc. • Measurements on Oct. 25 between noon and 2 PM at the same 21°/96° location but at an altitude of 11.5 km showed a concentration of 2 to 6 x 106 molecules per cc. Since hydroxyl radical is formed by the action of sunlight, concentration is highest at noon and the species disap pears at night. So to get background data, measurements were made at night at the same locations and altitudes as during the day. Hydroxyl radical wasn't detected. The Maryland scientists—Dr. Thomas
C&EN staff photo
Nobelists gather for Chemical Congress symposium A touch of Stockholm was visited on Mexico City as five Mexican, Canadian, and U.S. Nobel Lau reates convened to present a Chemical Congress symposium on expanding frontiers of science. Shown here at a press conference that pre ceded the symposium are (left to right) Dr. Donald A. Glaser (physics, 1960), professor of physics and molecular biology at the University of California, Berkeley; Dr. Gerhard Herzberg (chemistry, 1971), distinguished research scientist at the National Research Council, Ottawa, Canada; Dr. Severo Ochoa (medicine, 1959), of Roche Institute of Molecular Biology, Nutley, N.J.; Dr. Paul J. Flory (chemistry, 1974), professor of chemistry at Stanford University; and Dr. Glenn T. Seaborg (chemistry, 1951), university professor of chemistry and associate director of the Lawrence Berkeley Laboratory at the University of California, Berkeley. At the symposium, the Nobelists spoke on topics ranging from Herzberg's discussion of spectroscopic studies in astrochemistry to Glaser's presentation on biomolecular control and genetic tailoring.
Chemical Congress-Mexico
