NOVELTY - Closed system bioreactor apparatus comprises: (a) one or more flexible tubes capable of containing an aqueous medium; (b) one or more peristaltic rollers operably coupled to the tubes to circulate the medium through the tubes and to remove photosynthetically generated oxygen; and (c) a thermal barrier within the tubes to regulate the temperature of the medium, where the medium may be alternatively directed above or below the barrier to warm or cool the medium.    USE - The system, apparatus, and methods are useful for culturing algae and for producing useful products from algae, including biofuels (e.g. biodiesel, methanol, ethanol), bio-polymers, chemical precursors, and/or animal or human food. The algal culture can be used to provide animal or human food source, by culturing edible algae. It can also be used to support growth of a secondary food source, such as shrimp or other aquatic species that feed on algae.    ADVANTAGE - The closed system bioreactor apparatus greatly reduces problems from contaminating algae, algae consuming microorganisms, and/or other extraneous species. It also provides for improved thermal regulation designed to maintain temperature compatible with optimal growth and oil production. The apparatus and system are also constructed and operated on land that is marginal or useless for cultivation of standard agricultural crops. This bioreactor technology stabilizes algae cultivation temperature with low energy usage, which is practical on any scale. The apparatus and system creates high value products from algae that is largely fed by industrial, agricultural, and municipal waste products at an affordable cost.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a closed system bioreactor apparatus comprising two flexible tubes capable of containing an aqueous medium, two peristaltic rollers operably coupled to the tubes to circulate the medium through the tubes and to remove gas bubbles from the tubes, multiple axial vortex inducers vertically arranged within the tubes to provide rotational exposure of the aqueous medium to sunlight, and a first and a second control housing operably coupled to the ends of the tubes to form a closed system;    (2) culturing algae which comprises introducing algae in aqueous medium into the closed system bioreactor, exposing the algae to sunlight, regulating the temperature of the medium by controlling the distribution of medium above and below a thermal barrier and culturing the algae under conditions allowing algal reproduction and growth, and    (3) a system for producing biodiesel from algae which comprises a closed bioreactor containing a suspension of algae in aqueous medium, a mechanism for harvesting the algae from the medium, a device for separating oil from the algae and an apparatus for converting the oil into biodiesel.