UC Irvine

The well known algistatic effect of cationic surfactants was not exhibited by homologous series of amphoteric, anionic and non-ionic types assayed with Chlamydomonas reinhardi. Sulphobetaine amphoterics, 3-(octyl-octadecyldimethylammonio)-1-propanesulphonates, caused growth inhibition when the lipophile contained twelve or more carbon atoms, but only at micellar concentrations. Critical micelle concentration (CMC) of sulphobetaines decreases logarithmically with increasing alkyl chain length and derivatives having eight and ten carbons in the lipophile were below the CMC at the highest concentration tested. Despite their pronounced protein-denaturing properties, sodium higher alkylsulphates did not materially inhibit the growth of Chlamydomonas. This may be due to the fact that the Kraft points of these anionics having fourteen or more carbon atoms were above the culture temperatures, thereby reducing their solution properties. Although less inhibiting than the sulphobetains, the non-ionic alcohol ethoxylates decreased growth with increasing hydrophilicity. The most lipophilic non-ionic showed growth-promoting effects. © 1983.