Micro-organisms algae

Agar occurs as a cell-wall constituent of the red marine algae Rho ophyceae, from which it is extracted by hot water, and marketed as a dry powder, flakes, or strips. It dissolves in hot water and sets on cooling to a jelly at a concentration as low as 0-5%. Its chief uses are as a solid medium for cultivating micro-organisms, as a thickener, emulsion stabilizer in the food industry and as a laxative. 

Single cell protein, normally called simply SCP, is the term used to describe microbial cells, or proteins from them, which are used as food (food for humans) or feed (food for farm animals or fish). Although the term micro-organisms covers viruses, bacteria, fungi, algae and protozoa, viruses and protozoa are not considered suitable for SCP production. 

Micro-organisms are rich in protein. Microbial cells can contain as much protein as conventional foods. Bacteria can contain 60-65% (as a % of dry weight) protein whereas fungi and algae contain about 40%. In addition, microbial cells can be a rich source of fibre, unsaturated fats, minerals and vitamins. They are low in saturated fats and sodium. 

Item (1) is not always true. Some micro-organisms are easier to digest than plants, whereas others (such as algae) are more difficult to digest than many plant foods. 

Figure 8.13(a) Collection of published values for Cu" complexation equilibrium quotient (K) in various micro-organism systems (bacteria and algae) (adapted from Town and Filella, 1999). Symbols O, cells + exudates O, cells , exudates. 

Cullen et al. (1994) have proposed a possible mechanism of arsenic methylation after the study in which arsenite, arsenate, monomethyl-arsonate or dimethylarsinic acid were added to the growth medium in the presence of the unicellular alga Polyphsa peniculus. Evidence of arsenic biomethylation by the micro-organism Apiotrichum humicola in the presence of L-methionine-methyl-d3 has come from the same laboratory (Cullen et al., 1995). Their findings point to the role of S-adenosylmethionine, or a related sulfonium compound as possible methyl donors. Arsenic biomethylation and biotransformation has also been demonstrated in a freshwater environment (Kuroiwa et al., 1994). 

Very H-nch algae phyto- plankton micro- organisms amorphous H-nch Spores pollen cuticle amorphous H-Poor wood humic tissues coal amorphous NoH "Charcoal" oxidized tissues... 

S Biological corrosion. Damp masonry surfaces allow the growth of micro-organisms such as bacteria, moulds, mosses, algae and lichens (Figure 6.11). With an efficient metabolism the separation of the products of metabolism can result in the deposition of salts. If walls are not treated the effect is an uninhabitable building. 

Schneider, J., 1977. Carbonate construction and decomposition by epilithic and endo-lithic micro-organisms in salt- and freshwater. In E. Fliigel (Editor), Fossil Algae, Springer, Berlin, pp. 248—260. 

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