NOVELTY - Biofilm photobioreactor system comprises: a flexible film defining a photobioreactor enclosure; channels; a support substrate to form a biofilm; a photosynthetic, autofermentative microorganism forming a biofilm on the substrate; at least one port formed in the flexible film in fluid communication with the enclosure; at least one gas exhaust vent formed in the flexible film; gas comprising carbon dioxide that flows through the photobioreactor enclosure intermittently; a first liquid that at least partially fills the photobioreactor enclosure intermittently; and a second liquid.    USE - The biofilm photobioreactor system is useful for producing at least one chemical product consisting of biofuels or feedstocks, where the biofuel is ethanol, hydrogen, propanol or butanol, and the feedstock is acetate, lactate or formate (all claimed).    ADVANTAGE - The biofilm photobioreactor system: supports environmental conditions; has a design that enables increased uptake of carbon dioxide by the biofilm, increased removal of oxygen, improved genetic stability of the biofilm and improved stability of the chemical product, while mitigating toxicity effects of the chemical product on the biofilm and temperature effects on the biofilm; and maintains a low cost basis.    DETAILED DESCRIPTION - Biofilm photobioreactor system comprises: a flexible film defining a photobioreactor enclosure; channels defined by at least one partition disposed in the photobioreactor enclosure; a support substrate for the formation of a biofilm on it by a microorganism; a photosynthetic, autofermentative microorganism forming a biofilm on the support substrate; at least one port formed in the flexible film that is in fluid communication with the photobioreactor enclosure; at least one gas exhaust vent formed in the flexible film that is in fluid communication with the photobioreactor enclosure; gas comprising carbon dioxide that flows through the photobioreactor enclosure intermittently during the photosynthesis phase; a first liquid that at least partially fills the photobioreactor enclosure intermittently during the photosynthesis phase; and a second liquid that at least partially fills the photobioreactor enclosure during the autofermentation phase. The channels are in fluid communication. The support substrate is disposed in the channels and is fixed to the flexible film and/or the partition. The photosynthetic, fermentative microorganism makes at least one metabolic intermediate compound during a photosynthesis phase and converts the metabolic intermediate compound to at least one chemical product during an autofermentation phase. The gas enters the photobioreactor enclosure through the port, contacts the biofilm and leaves the photobioreactor enclosure through the gas exhaust vent. The first liquid enters the photobioreactor enclosure through the port, contacts the biofilm and leaves the photobioreactor enclosure through the port. The second liquid enters the photobioreactor enclosure through the port, contacts the biofilm and leaves the photobioreactor enclosure through the port. The chemical product made by the biofilm during the autofermentation phase enters the second liquid. The photobioreactor enclosure has a flat panel shape and at least one portion of the flexible film is translucent. INDEPENDENT CLAIMS are also included for:    (1) a flat panel biofilm photobioreactor system comprising many channels in fluid communication that are adapted to admit light, inlets and outlets adapted to admit flow of a gas comprising carbon dioxide and flow of a liquid into and out of the channels, a formation surface disposed in the channels and a photosynthetic, autofermentative microorganism that makes a chemical product through autofermentation and forms a biofilm on the formation surface, where the channels are formed in an enclosure enclosed by a flexible film, the formation surface is fixed to the flexible film, the gas comprising carbon dioxide and the liquid contact the biofilm and the chemical product enters the liquid; and    (2) making at least one chemical product comprising exposing a biofilm comprising a photosynthetic, autofermentative microorganism to light, where the biofilm is disposed on a support substrate that is disposed in channels of a biofilm photobioreactor and the support substrate is fixed to inner surfaces of the biofilm photobioreactor, alternately flowing a gas comprising carbon dioxide through the channels and at least partially filling the channels with a first liquid, where the gas comprising carbon dioxide and the first liquid contact the biofilm and the photosynthetic, autofermentative microorganism makes at least one metabolic intermediate compound by photosynthesis, depriving the biofilm of light and at least partially filling the channels of the biofilm photobioreactor with a second liquid, where the second liquid contacts the biofilm, the photosynthetic, autofermentative microorganism converts the metabolic intermediate compound into the chemical product and the chemical product enters the second liquid.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of an array of at panel photobioreactors and a mounting system.    Array (220)    Side supports (500)    Mounting system (510)    Motor (520)    Adjustment arms (530)