basic liquid medium for fermenter cultivations is given in table i see also the experimental section below the reactor shouldn 39 t be equipped with any type of baffle or internal component causing extensive turbulence and agitation must be provided in a very mild way for instance by gas lift or by any other type of impeller able to achieve good mixing without generating shear forces this is of crucial importance in order to obtain very high molecular weights and is contrary to the recommendation given in u s pat no 4 784 990 that is u201c growing with vigorous agitation a microorganism of the genus streptococcus u201d various culture alternatives have been tested and found to work for instance batch fed batch semicontinuous fed batch and continuous cultivation the standard agar plates used where blood agar ba prepared from horse blood at the central bacteriolgical laboratory lu bacto todd hewitt agar tha difco and tysa made from 10 g l bacto tryptone difco 1 g l bacto yeast extract difco 1 6 g l disodium hydrogen phosphate merck pa 2 g l sodium hydrogen carbonate merck pa 0 1 g l magnesium sulphate merck pa 20 g l bacto agar difco and 8 g l sucrose bdh liquid medium for initial tests was todd hewitt broth difco supplemented with bacto yeast extract as above chemical mutagenesis with nitrosoguanidine sigma was employed cerda olmedo i e and hanwalt p c 1968 the wild type strain was spread on a tysa plate a few crystals of nitrosoguanidine was applied in the center after incubation a clear zone of inhibition was evident around the nitrosoguanidine crystals mucoid colonies growing out in the vicinity of the zone edge were selected.