OBJECTIVETo determine the physicochemical properties of the mutanase of Trichoderma harzianum isolated from China and to study the influence of mutanase on the adherence of oral Streptococci and the structure of oral biofilms.

METHODSSix fungal strains belonging to Trichoderma were tested for mutanase production in the same cultural condition, the strain producing the highest mutanase activity was studied further and the pH and temperature optimum of the enzyme was determined. The RT-PCR method was used to obtain the gene coding for mutanase and the product was cloned to pMD18-T simple vector for sequencing. Inhibition effects of mutanase on the adherence of Streptococcus sobrinus OMZ176, Streptococcus sobrinus 6715, Streptococcus mutans MT8148 were studied by adherence test. The optical sectioning of biofilms with or without mutanase supplementation were analyzed by confocal laser scanning microscopy (CLSM).

RESULTSThe highest enzymatic activity was achieved by Trichoderma harzianum Th1, the maximum activity was at pH 5.5 and at 40 degrees C. The nucleotide sequence was 92% homology with that of a known gene coding a mutanase (GenBank accession No. AJ243799). The adherence of Streptococcus sobrinus OMZ176, Streptococcus sobrinus 6715, Streptococcus mutans MT8148 was significantly inhibited by mutanase. Compared with control, the biofilms with mutanase supplementation had lower height and sparser structure.

CONCLUSIONSThe mutanase from Trichoderma harzianum Th1 can inhibit the adherence of oral Streptococci and had an influence on the structure of oral biofilms.