Two-stage process for producing oil from microalgae

Abstract

A process for production of biofuels from algae can include cultivating an oil-producing algae by promoting sequential photoautotrophic and heterotrophic growth. The method can further include producing oil by heterotrophic growth of algae wherein the heterotrophic algae growth is achieved by introducing a sugar feed to the oil-producing algae. An algal oil can be extracted from the oil-producing algae, and can be converted to form biodiesel.

1 - 17 . (canceled) 
     
     
         18 . A process for production of biofuel from algae, comprising:
 a) cultivating a carbohydrate-producing algae by autotrophic growth in a first stage;   b) shifting growth from autotrophic growth to heterotrophic growth by inducing stress in the carbohydrate-producing algae in a second stage;   c) extracting carbohydrates from the starch-producing algae; and   d) utilizing the carbohydrate as a component of biofuel production.   
     
     
         19 . The method of  claim 18 , wherein the inducing stress is accomplished with a stress induction mechanism selected from the group consisting of: light deprivation; nutrient deprivation; injection of reactive oxygen; or chemical additives. 
     
     
         20 . The method of  claim 19 , wherein the nutrient deprivation is deprivation of either nitrogen or phosphorous or both nitrogen and phosphorous. 
     
     
         21 . The method of  claim 19 , wherein the reactive oxygen is ozone or peroxide or both ozone and peroxide. 
     
     
         22 . The method of  claim 19 , wherein the stress induction mechanism is a combination of light deprivation and nutrient deprivation. 
     
     
         23 . The method of  claim 18 , wherein shifting from autotrophic growth to heterotrophic growth arrests production of green mass and biologically converts to filling of algae cell bodies with carbohydrates. 
     
     
         24 . The method of  claim 23 , wherein the autotrophic growth and heterotrophic growth overlap. 
     
     
         25 . The process of  claim 18 , wherein the carbohydrate-producing algae includes a member selected from the group consisting of diatoms (bacillariophytes), green algae (chlorophytes), blue-green algae (cyanophytes), golden-brown algae (chrysophytes), haptophytes, and combinations thereof. 
     
     
         26 . The process of  claim 25 , wherein the carbohydrate-producing algae includes  Amphipleura, Amphora, Chaetoceros, Cyclotella, Cymbella, Fragilaria, Hantzschia, Navicula, Nitzschia, Phaeodactylum, Thalassiosira, Ankistrodesmus, Botryococcus, Chlorella, Chlorococcum, Dunaliella, Monoraphidium, Oocystis, Scenedesmus, Tetraselmis, Oscillatoria, Synechococcus, Boekelovia , or combinations thereof. 
     
     
         27 . The process of  claim 26 , wherein the carbohydrate-producing algae includes  Chlorella, Dunaliella , or combinations thereof. 
     
     
         28 . The process of  claim 18 , further comprising converting the carbohydrates to sugar. 
     
     
         29 . The process for  claim 28 , further comprising utilizing the sugar in a fermentation process to produce alcohol. 
     
     
         30 . The process of  claim 29 , further comprising recovering the alcohol as the biofuel. 
     
     
         31 . The process of  claim 28 , further comprising employing the sugar as a feed for heterotrophic growth of an oil-producing algae. 
     
     
         32 . The process of  claim 31 , wherein the sugar feed is the primary source of both carbon and energy in the heterotrophic growth stage. 
     
     
         33 . The process of  claim 32 , wherein the heterotrophic growth stage of the carbohydrate-producing algae is initiated using a stress induction mechanism. 
     
     
         34 . The process of  claim 33 , wherein the stress induction is a member selected from the group consisting of: light deprivation, nutrient deprivation, injection of a reactive oxygen source, a lipid trigger, or a chemical additive. 
     
     
         35 . The process of  claim 28 , wherein the heterotrophic growth stage of the carbohydrate-producing algae is preceded by an autotrophic growth stage of the oil-producing algae.