Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1983-06-07
1985-11-19
Evans, J. E.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
47 14, 426429, 426431, 568869, 585809, 585811, 585829, C07C 2976, C12N 102, A01D 4400, B01D 1508
Patent
active
045543909
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method for harvesting algae from salt solutions and especially to the harvesting of halotolerant unicellular algae belonging to the genus Dunaliella. The invention also relates to the recovery of carotenes, especially .beta.-carotene, chemically related carotenoids, triterpenes, glycerol and proteinaceous material from the harvested algae.
Algae which contain carotenes, carotenoids and triterpenes commonly occur as a natural growth in saline lakes and lagoons. Such algae may also occur naturally and/or may be cultivated in saline ponds, such as those used in conjunction with solar evaporation complexes, which may also include means for varying the content of carbon dioxide in the water in order to control or enhance growth of the algae. The saline material or salt solutions containing the algae are commonly referred to as "brine".
The carotenes, carotenoids and triterpenes in the algae may be recovered from same in the form of a liquid or as pure and crystalline materials defined as "carotene". This is a mixture comprising mainly .beta.-carotene and its isomers and similar substances. Carotene is of value as a source of pro-vitamin A, which is converted in the human body to vitamin A, and as a natural food colouring agent for use, for example, in the colouring of margarine, soft drinks and other edible products.
The investigations of carotene-rich algae upon which this specification is based have been particularly directed to the species Dunaliella salina. It is to be understood, however, that the invention is also applicable to other algae which may have an economically recoverable carotene content.
Algae may be recovered from brine by various flotation processes. These processes all include steps in which the algal cells are subject to disintegration. This disintegration is found necessary to float the algal material to the surface of the brine. However, the need for disintegration of the algal cells and for the introduction of finely dispersed air bubbles to assist flotation of the algal material places relatively high energy requirements on the process and also leads to oxidation of the caroteniferous materials in the algal cells. (The term "caroteniferous materials" is used herein to cover both carotenes and carotenoids.) It has also been found that by using the flotation process outlined, the recovery of only approximately 70% of the algae present in the brines is obtained.
Algae of the genus Dunaliella are known to contain .beta.-carotene and to consist of motile single cells 10-20 .mu.m in diameter and having a specific gravity of about 1.1. As a consequence of their low specific gravity the cells do not readily sediment, especially from brines whose specific gravity is greater than unity. The algae can contain up to 50 percent of their dry weight of glycerol and up to 10 percent of their dry weight of .beta.-carotene when grown in sodium chloride solution of 3M concentration. They occur naturally at concentrations of about 50 mg/litre in the brine pools of salt fields but concentrations of about 300 mg/litre can be attained when the algae are grown in specially constructed ponds.
The prior art has been mainly directed towards the growth of the organisms and to the use of centrifugal and filtration methods to separate and concentrate the organisms from the nutrient brine in which they have been grown. In U.S. Pat. Nos. 4,115,949 (corresponding to Australian Patent Application No. 25,773/77) and 4,199,895 Avron and Ben-Amotz disclose a process for the simultaneous production of glycerol, .beta.-carotene and a protein-rich material of nutritive value from algae of the genus Dunaliella. The algae are grown under controlled conditions in a nutrient medium, initially at a sodium chloride concentration of at least 1.5M and later at a sodium chloride concentration of at least 3M. The algae are harvested by a variety of means such as sedimentation, flocculation, filtration or centrifugation. Further centrifugation is then used to concentrate the algae prior to the extraction of
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The Merck Index, Ninth Edition, (1976), p. 237.
Curtain Cyril C.
Snook Harvey
Betatene Limited
Commonwealth Scientific and Industrial Research Organization
Evans J. E.
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