Abstract: A method for rupturing microalgae in an aqueous suspension is disclosed. In one embodiment the aqueous suspension is passed through a constriction into a liquid phase at a pressure sufficient to rupture the cells by circulating the aqueous suspension through a constriction in a pump loop at a pressure and a percent recycle sufficient to rupture the cells. Cells of the alga Dunaliella salina can be ruptured by the method of the invention to promote froth flotation and mechanical filtration of the cells for recovery of mixed carotenoids.

Abstract: A process and system are disclosed for recovering mixed carotenoids from the alga Dunaliella salina. The harvested cells are ruptured, typically by circulating the algal suspension at high pressure through a pump loop. The cells can then be dewatered by absorptive bubble separation techniques, including a froth floatation circuit that has a roughing zone and a concentrating zone. If further concentration is desired, the algal concentrate can be mechanically filtered in a cross flow microfiltration unit in the absence of flocculating agents with substantially no loss of carotenoids in the permeate. Various methods for extracting mixed carotenoids and other components from the algae are disclosed, including dense gas extraction, and extractions with natural and synthetic flavorants, and edible oils.

Abstract: A process for dewatering an aqueous suspension of microalgae is disclosed in which the aqueous suspension of the algae is introduced into a bubble column or a modified bubble column for generating a froth of bubbles and adsorbed algal cells that can be separated from the aqueous suspension. In one advantageous embodiment, the bubble column is a multi-stage loop-flow flotation column that has three loop-flow zones, each of which is defined by a draft tube concentrically mounted in the column to divide each loop-flow zone into a riser and the downcomer. Fine bubbles of gas and brine are in cocurrent upward flow in the riser and in cocurrent downward flow the downcomer. A higher gas holdup is promoted in the riser than in the downcomer, thereby circulating the brine in loop-flow upwardly through the riser and downwardly through the downcomer. Liquid communication between adjacent loop-flow zones is substantially eliminated. A froth enriched in algae is generated that can be separated from the aqueous suspension.

Abstract: Methods are disclosed for dewatering an aqueous suspension of microalgae, especially Dunaliella salina, with a Jameson cell. The algal cells are ruptured sufficiently to promote froth flotation of the cells from the suspension. The algal suspension is introduced into the top of the Jameson cell downcomer and passed through an orifice plate therein to generate a free liquid jet of the suspension. The jet is plunged downwardly through a gas and the gas is transported with the jet through a gas and liquid interface into the algal suspension. The momentum of the jet is dissipated, which disperses the gas into fine bubbles. The fine bubbles are intimately contacted with the aqueous suspension in cocurrent downward flow in a collection zone to absorb the algal bodies onto the surfaces of the bubbles. A froth of bubble and algal agglomerates is formed and collapsed to obtain a dewatered algal concentrate.