The wood-degrading basidiomycete Cerrena unicolor C-139 has been suggested as a potential producer of the industrially important enzyme laccase. Basic culture parameters influencing the enzyme synthesis in shakenflask and aerated bioreactor cultures were evaluated to improve the yields of the process. Production of extracellular laccase was considerably enhanced by the addition of Cu 2+ in the micromolar range to a carbon-sufficient and nitrogen-sufficient culture medium (C/N = 16.69). When an optimised medium containing glucose (10 g/L) and L-asparagine (1.5 g/L) was used, and enzyme synthesis was stimulated by addition of 10 lM Cu 2+ to the culture medium on days 3, 6 and 9, maximal laccase productivity obtained after 17 days' cultivation in shaken flask cultures was above 100,000 nkat/L. In fermenter fungal cultures, the influence of stabilisation of medium pH on laccase activity was additionally studied. The use of a bioreactor with an automatic pH control set at pH 6.5 after 48-h incubation resulted in the enzyme activity of 65,000 nkat/L after 8 days' cultivation.

Of the three cariogenic streptococci grown in four various culture media, the strain Streptococcus mutans 20381 was found to produce large amounts of extracellular glucosyltransferase and water‐insoluble, adhesive exopolysaccharide when grown in batch culture on brain‐heart infusion broth. Methylation and nuclear magnetic resonance analyses revealed that the insoluble polymers synthesized by the crude glucosyltransferase preparations were mixed‐linkage (1 → 3), (1 → 6)‐α‐D‐glucans (so‐called mutans) with a greater proportion of 1,3 to 1,6 linkages and major branch points of 3,6‐linked glucose. The percentage content of different types of linkages in glucans varied widely and depended on the strain of cariogenic bacteria used to produce glucosyltransferase, and on the kind of medium utilized to cultivate mutans streptococci. The potential application of insoluble glucan produced by mutans streptococci is discussed.

No abstract

No abstract

No abstract