Chlorella vulgaris: A species of green microalgae in the family Chlorellaceae. It is used as a model organism for PHOTOSYNTHESIS, and as a food supplement (DIETARY SUPPLEMENTS).Chlorella: Nonmotile unicellular green algae potentially valuable as a source of high-grade protein and B-complex vitamins.Piper betle: A plant genus of the family PIPERACEAE that is indigenous in the Indian Malay region and cultivated in Madagascar, and the West Indies. It contains chavibetol, chavicol and cadinene. The leaf is chewed as a stimulant, antiseptic and sialogogue. The common name of betel is also used for ARECA.Nitrate Reductase (NADH): An NAD-dependent enzyme that catalyzes the oxidation of nitrite to nitrate. It is a FLAVOPROTEIN that contains IRON and MOLYBDENUM and is involved in the first step of nitrate assimilation in PLANTS; FUNGI; and BACTERIA. It was formerly classified as EC 22.214.171.124.Photobioreactors: Devices for generating biological products that use light as the energy source. They are used for controlled BIOMASS production such as growing cyanobacteria, mosses, or algae.Nitrate Reductases: Oxidoreductases that are specific for the reduction of NITRATES.Microalgae: A non-taxonomic term for unicellular microscopic algae which are found in both freshwater and marine environments. Some authors consider DIATOMS; CYANOBACTERIA; HAPTOPHYTA; and DINOFLAGELLATES as part of microalgae, even though they are not algae.Tocotrienols: Natural analogs of TOCOPHEROLS exhibiting antioxidant activity. These tocol derivatives and isomers contain a benzopyran ring and an unsaturated isoprenoid side chain.Phycodnaviridae: A family of DNA plant viruses that infect eukaryotic algae.Eukaryota: One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.Nitrate Reductase: An enzyme that catalyzes the oxidation of nitrite to nitrate. It is a cytochrome protein that contains IRON and MOLYBDENUM.Algal Proteins: Proteins found in any species of algae.Proteus vulgaris: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria that occurs in soil, fecal matter, and sewage. It is an opportunistic pathogen and causes cystitis and pyelonephritis.Desulfovibrio vulgaris: A species of gram-negative, anaerobic, rod-shaped bacteria isolated from soil, animal intestines and feces, and fresh and salt water.Plant Extracts: Concentrated pharmaceutical preparations of plants obtained by removing active constituents with a suitable solvent, which is evaporated away, and adjusting the residue to a prescribed standard.