The extracellular polysaccharides produced by Cryptococczrs lazrrenlii have been isolated and shown to consist of (A) a n acidic polysaccharide containing D-mannose, D-xylose, and D-glucuronic acid; ( B ) a neutral polysaccharide containing D-glucose only.Preliminary structural studies on the acidic material suggest that it consists of a mannosecontaining backbone with xylose and glucuronic acid as end groups, \vhile the glucan contains 1 -,3 3, 1 --t 4, 1 --t 2, and (or) 1 --t 6 linked residues. INTRODUCTION l/Iucli is l t n o~~~n about the origin of sugars fouiid in ho~~~opolysaccharides (1-11). On the other halid the origin of sugars in heteropolysaccharides has not been investigated to any great extent (12, 13).As part of a program for iiivestigatiiig the biosynthesis of monosaccliarides found in heteropolysaccl~arides, we have studied the extracellular polysaccharide produced by the yeast orgallisill Cryptococc~ls lar~rentii.This organism, 1;indly supplied by the United States Department of Agriculture, Peoria, Illinois, was chosen because it produced high yields of polysaccharides froin a wide variety of sugar substances.Cryfltococc~~s laz~rentii \\.as grown 011 an unbuffered casaiiiiiio acids -salts medium n~i t h glucose as the main carbon source (14). An acidic and a neutral polysaccharide were isolated by the follo\\~ing procedure, which was considered unlil
Products of the thermal and photosensitised autoxidation of N-alkyl-and NN-dialkyl-amides have been identified. N-n-Alkylamides yield principally N-acylamides. primary amides, and N-formylamides, as a result of initial abstraction of a hydrogen atom from the carbon adjacent to nitrogen. Formation of N-formylamides, and of Nacylamides from N-s-alkylamides, . involves C(l)-C,zl bond scission in an N-alkyl group. Oxidation of NNdialkylamides follows a similar pattern. Gas-liquid-chromatographic retention data are presented for 89 amides.
Soluble methane monooxygenase (sMMO) from methane-oxidising bacteria can oxygenate more than 100 hydrocarbons and is one of the most catalytically versatile biological oxidation catalysts. Expression of recombinant sMMO has to date not been achieved in Escherichia coli and so an alternative expression system must be used to manipulate it genetically. Here we report substantial improvements to the previously described system for mutagenesis of sMMO and expression of recombinant enzymes in a methanotroph (Methylosinus trichosporium OB3b) expression system. This system has been utilised to make a number of new mutants and to engineer sMMO to increase its catalytic precision with a specific substrate whilst increasing activity by up to 6-fold. These results are the first ‘proof-of-principle’ experiments illustrating the feasibility of developing sMMO-derived catalysts for diverse applications.
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