STARCH PRODUCTION IN THE GENUS TRICHOSPORON
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Reduced copper is deposited on the anion exchange resin by treatment with a cupric salt followed by an alkaline reduction. The resulting metal-resin complex reacts readily with dissolved oxygen in much the same manner as the familiar cuprous copper-ammonia solutions which have been used for oxygen removal in gas analysis. The advantage of the metal-resin complex is its very small dissociation in neutral or alkaline media. Consequently, there is negligible leakage of harmful copper ions into properly buffered media. The anion exchange resin used in these experiments, "duolite S-10," must be reactivated before use since it is in the oxidized state when received. This may be conducted easily in the laboratory by first soaking and washing the resin with distilled water. Each 500 ml portion of wet resin is then treated with two liters of a solution containing 0.5 M sodium hydrosulfite and 1.25 M sodium hydroxide. Apparently, sodium hydrosulfite is the only appropriate reducing agent. Each 500 ml portion of wet resin is then washed with approximately 5 liters of distilled water which has been previously boiled to remove oxygen. The reactivation steps may be conducted either in a continuous column or in beakers by adding successive small portions of liquid with stirring followed by decantation. The reduced resin, which has undergone a color change from a blue-green in the oxidized state to a metallic purple in the reduced state, is then stored under oxygen-free water until used. It is felt that there are many special cases of anaerobic growth problems to which the use of the resin may be applied.