Maize kemals

The subsequent advance was rather fortuitous and rested more with serendipity than with scientific logic. A search was made for cheaper more effective replacements for casein hydrolysate. Amongst the tested materials was com steep liquor (CSL). CSL is a by-product of the manufacture of starch from maize kemals. Whole maize is incubated in warm water, at 50°C acidified with SO2. Thermophilic bacteria hydrolyse proteins and other components of the kemals, thereby loosening the starch granules. These are removed, leaving behind the steep liquor which is used to treat further maize kemals. Ultimately, the liquor is too viscous to re-use and the liquor is concentrated and used as cattle feed. It was this material that was used for penicillin fermentation. Surprisingly, the yield of penicillin increased by a further 5-10 fold giving yields of 50-100 ig ml. 

In further experiments,185 it was found that DU1 was one of the two major soluble starch synthases, and when the C-terminal 450 residues of DU1 were expressed in E. coli, it was shown to have SS activity. Of interest was that antisera prepared against DU1 detected a soluble protein in endosperm extracts of molecular size greater than 200 kDa that was absent in dul mutants.185 The antisera reduced starch synthase activity by 20-30% in kemal extracts. In the same study, antisera prepared against SSI reduced starch synthase activity by 60%. In dul mutants, antisera prepared against SSI reduced the SS activity essentially to zero, suggesting that SSI and SSII were the only maize endosperm soluble starch synthases. Because of the high similarity in sequence of the DU1 starch synthase II to the potato SSIII, and because both are exclusively soluble, it is argued that DU1 is the evolutionary counterpart of potato SSIII.185,188 206 It is proposed that DU1 and maize SSII should be known as maize SSIII.184... 

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