Production of biopharmaceuticals Genetically engineered
C. reinhardtii has been used to produce a mammalian serum amyloid protein (needs citation), a human
antibody protein (needs citation), human
Vascular endothelial growth factor, a potential
therapeutic Human Papillomavirus 16 vaccine, a potential
malaria vaccine (an
edible algae vaccine), and a complex designer drug that could be used to treat cancer.
Alternative protein source C. reinhardtii has been suggested as a new algae-based nutritional source. Compared to
Chlorella and
Spirulina,
C. reinhardtii was found to have more Alpha-linolenic acid, and a lower quantity of heavy metals while also containing all the essential amino acids and similar protein content. Triton Algae Innovations was developing a commercial alternative protein product made from
C reinhardtii.
Clean source of hydrogen production In 1939, the German researcher
Hans Gaffron (1902–1979), who was at that time attached to the University of Chicago, discovered the hydrogen metabolism of unicellular green algae.
C reinhardtii and some other green algae can, under specified circumstances, stop producing oxygen and convert instead to the production of hydrogen. This reaction by
hydrogenase, an
enzyme active only in the absence of oxygen, is short-lived. Over the next thirty years, Gaffron and his team worked out the basic mechanics of this photosynthetic hydrogen production by algae. The circumstances in which these algae switch to producing hydrogen instead of oxygen are the lack of
sulfur. To increase the production of hydrogen, several tracks are being followed by the researchers. • The first track is decoupling hydrogenase from photosynthesis. This way, oxygen accumulation can no longer inhibit the production of hydrogen. And, if one goes one step further by changing the structure of the enzyme hydrogenase, it becomes possible to render hydrogenase insensitive to oxygen. This makes a continuous production of hydrogen possible. In this case, the flux of electrons needed for this production no longer comes from the production of sugars but is drawn from the breakdown of its own stock of
starch. • A second track is to interrupt temporarily, through
genetic manipulation of hydrogenase, the photosynthesis process. This inhibits oxygen's reaching a level where it is able to stop the production of hydrogen. • The third track, mainly investigated by researchers in the 1950s, is chemical or mechanical methods of removal of O2 produced by the photosynthetic activity of the algal cells. These have included the addition of O2 scavengers, the use of added reductants, and purging the cultures with inert gases. However, these methods are not inherently scalable, and may not be applicable to applied systems. New research has appeared on the subject of removing oxygen from algae cultures, and may eliminate scaling problems. • The fourth track has been investigated, namely using copper salts to decouple hydrogenase action from oxygen production. • The fifth track has been suggested to reroute the photosynthetic electron flow from fixation in
Calvin cycle to hydrogenase by applying short light pulses to anaerobic algae or by depleting the culture of . Under pulse-illumination conditions, algae produce H2 via the most efficient mechanism of direct water biophotolysis, proceeding in two distinct steps: 1.
Photosystem II-dependent water oxidation reaction: 2H2O → 4H+ + O2 + 4e⁻; 2.
Hydrogenase-dependent reversible reduction of protons to molecular hydrogen: 4H+ + 4e⁻ ⇄ 2H2. If the water oxidation reaction leading to O2 production is balanced with O2 consumption, either by respiration or by introducing additional O2 absorbents or scavengers, the photosynthetic production of H2 can be sustained for a prolonged period. This balance prevents the inhibition of hydrogenase activity by accumulated O2, ensuring steady hydrogen production under these optimized conditions. ==See also==