Submitted to: Journal of Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/1998
Publication Date: N/A
Citation: N/A Interpretive Summary: Flax (Linum usitatissimum L.), which is the source of linen, is an environmentally friendly crop to grow (i.e., little fertilizer, herbicide, and insecticide required). At the same time, the US is one of the largest per capita consumers of flax/linen fiber, and there is commercial interest in having a domestic source of flax fiber. The major problem in processing gflax to linen is retting, which is the microbial process for separating fibers from non-fiber tissues in the stems. Collaborative research between the Russell Research Center and the Dept. of Biochemistry, University of Georgia, through an NRI grant resulted in new fungal sources of enzymes that efficiently retted flax. This work addresses several priority areas of ARS research, i.e., environmentally friendly processing, value-added agricultural crops, global competitiveness, and rural development. The data provide information towards the goal of developing a US flax/linen industry and also provide fundamental information towards developing a strategy to optimize enzymatic retting of flax.
Technical Abstract: 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 40øC. The enzyme mixture in the filtrates of cultures grown on citrus-pectin appeared to contain relatively few protein according to 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 flax.