Method of microalgal biomass processing for high-value chemicals production, the resulting composition of butyrogenic algal slowly fermenting dietary fiber, and a way to improve colon health using a slowly fermenting butyrogenic algal dietary fiber

A method to extract and isolate compounds from an algal biomass comprising:

• physically treating the algal biomass by micro fluidization or ultra-sonication with a frequency greater than 20 KHz using a probe-type sonication or bath sonication, optionally in combination with extrusion using an extruder or with addition of a solvent, wherein the solvent is hexane, followed by centrifugation, wherein centrifugation was performed at a speed of about 500 rpm to about 15000 rpm, wherein centrifugation was performed at a speed of about 1000 rpm to about 10000 rpm, wherein centrifugation was performed at a speed of about 2000 rpm to about 5000 rpm, followed by
• extracting lipids and other oils from the top, the water soluble chemicals from the middle and the pellet from the bottom,
• hydrothermally treating the pellet by heating at high pH, optionally in combination with high pressure, while stirring, followed by
• centrifugation of the hydrothermally treated pellet at 2500 rpm for 10 minutes or 4000 rpm for 15 min,
• separating the supernatant from the resulting residue,
• precipitating water-soluble polysaccharides from the supernatant, wherein the precipitated polysaccharides were washed and pH adjusted to about 7, and dried,
• extracting carotenoids from the resulting residue using solvent.