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Food and fuel for a growing world

Past aquatic micro-organisms gave us oil and gas, so how can we stop trading on past sunlight to use algae in today's world? Algae provide food, vitamins, cosmetics and colourants, as well as a range of biofuel sources and substitutes for plastics and gels. These algal products show how useful these organisms can be for mankind.
  • Food: not just a wrapping for sushi, algae are used in sweets, chocolate milk and that welsh delicacy laverbread.

  • Health and beauty: Colouring for cosmetics, stabilisers for toothpastes and food supplements all come from algae.

  • Gels: Agar has uses from setting agents for jams, jellies and ice-creams, to growing microbes or separating DNA in the lab.

  • Fertilisers and chemicals: from seaweed extracts to specialist compounds.


Algae as bio-batteries

Biological Photovoltaic (BPV) cells offer an exciting opportunity to use algae to harvest sunlight and generate electricity. Algae-powered BPV cells work like a conventional battery. Sunlight can be captured by algae and used as a source of renewable energy. The advantages compared to conventional solar panels are that these are cheap, green, long lasting, environmentally friendly, and easy to manufacture.

Biofuels: harvesting sunlight to replace fossil fuels

Bioreactors or open ponds are needed to grow algae commercially. Biomass produced from fast growing algal offers many ways to generate energy - such as digestion for biogas or simply burning for combined heat and power. Oils are produced by many algae as storage reserves, and these can be extracted and refined to make biodiesel. Hydrogen is produced when green algae are starved of resources like sulphur, and have plenty of starch reserves.

Even algae need their vitamins!

All life needs vitamins - some were needed by the first life on earth. Vitamins provide cofactors that many enzymes need to work. Humans need vitamins for a healthy life - we can get this from eating lots of fresh fruit and vegetables. Mineral supplements: one vitamin not made by plants is vitamin B12 (cobalamin), which many algae contain in high levels, but they need an external supply like humans! Bacteria to the rescue: algae rely on bacteria in their growth media to provide vitamin B12. This association or 'symbiosis' was found in our laboratories, and shows how we rely on both algae and bacteria for vitamins.

Amazing marine and freshwater diversity

Microscopic phytoplankton blooms sequester one third of carbon emissions each year, and feed the aquatic food chain from shrimps to whales. Macroalgae (seaweeds) are found in the sea and on the seashore - in rockpools we readily spot green, red and brown fronds. There are an incredible array of algae, from dancing colonies of Volvox, diverse dinoflagellates, stunning diatoms and chalk-forming coccolithophorids, to enormous kelp forests in all aquatic environments.

Major groups of algae

  • Green algae (Chlorophytes): many live in fresh water - rivers, ponds and soil - ranging from Chlamydomonas and dancing Volvox to the sea lettuce Ulva.

  • Red algae (Rhodophytes): good to eat: Porphyra yezoensis or "nori" is used to wrap sushi, whilst dulse and laverbread are traditionally eaten in the UK.

  • Brown algae: many seaweeds like common bladderwrack and giant kelp. Their tiny relatives include diatoms and dinoflagellates, and even the terrible malarial parasite Plasmodium.

Pigments harvest light energy

  • Chlorophylls: algae trap light energy using chlorophylls, helped out by accessory pigments.

  • Fucoxanthins: xanthophyll accessory pigments found in brown macroalgae and diatoms.

  • Phycobilins: these pigments are on membrane surfaces of red algae and cyanobacteria, redistributing light energy to the chlorophylls beneath.

  • Blooms: the swirls of algal blooms are visible from space, often detected by increased chlorophyll in the sea. Phytoplankton bloom when nutrients, light and temperature are optimal (some are blooming poisonous).

Photosynthesis: the algal powerhouse

  • Carbon capture: using energy from sunlight, algae split water to release O2 and fix CO2 from the atmosphere for growth.

  • Rubisco: the enzyme that fixes CO2 - is the most abundant enzyme on Earth. Packaged into a pyrenoid in many algae.

  • A big fix: although their biomass is tiny relative to land plants, algae remove their own weight of carbon (3 Gt or 3 Thousand Million tonnes) from the atmosphere each year.

  • Little and large: picophytoplankton are only 2μm in diameter, but are vital for the marine food supply chain, whilst giant kelp are up to 60m in length.

  • Asynchronised swimmers: the beating flagella that help algae change direction are like cilia in our lungs, and can be models for human disease studies.

Symbioses: mutualistic exchanges give self support

  • Corals: the coralline skeleton is secreted by a polyp, but the beautiful colours of corals are due to their symbiotic zooxanthellae, which are dinoflagellates.

  • Sea Slugs: some gastropods graze on algae and take up the photosynthetically active chloroplasts.

  • Lichens: partnerships between green microalgae (or cyanobacteria) and fungi, lichens are sensitive indicators of pollution and are a vital part of the arctic tundra.

  • Endosymbioses: the earliest marine organisms were green and red algae, formed as as a photosynthetic cyanobacterium was engulfed by another organism; other endosymbiotic exchanges led to the huge microalgal diversity.