Production of highly efficient enzymes for flax retting by Rhizomucor pusillus

The fungus Rhizomucor pusillus grew well on flax (Linum usitatissimum L.) stems and on pectin as the sole source of carbon. Of several fungal isolates from dew-retted flax: R. pusillus produced enzyme filtrates that were the most effective in retting flax as evaluated by the Fried test. Addition of the chelator oxalic acid enhanced the retting efficiency of culture filtrates from the fungal isolates, with those of R. pusillus giving the highest degree of retting, Approximately one tenth of the protein concentration of R. pusillus as that of the commercial product Flaxzyme produced the same degree of flax retting. The culture filtrate of R pusillus contained high levels of pectinase activity, low levels of pectin methyl esterase activity, low cellulase and mannase activities, and no pectin lyase or xylanase activities. In our assay, pectinase activity was highest at pH 6.0 and 40 degrees C. The enzyme mixture in the filtrates of cultures grown on citrus-pectin appeared to contain relatively few proteins according to sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. R, pusillus produces a simple and efficient enzyme mixture that could provide an opportunity to determine the contribution of specific enzymes to flax retting. Results further suggest that hemicellulase and cellulase may not be required to ret flax. These studies provide information on enzymes towards the goal of developing a commercial process for enzymatic retting of Bar. Published by Elsevier Science B.V.