Enzymatic treatment of flax for use in composites

Enzymes are highly advantageous compared to dew retting to reach fibers of high and consistent quality. However, no unambiguous insights have been retained from the research, i.e. lacking a clear directive of which enzyme activities are strictly needed. Methods for evaluating enzymatic retting should be standardized, with characterization of chemical, morphological and mechanical properties and analysis of the ease of extraction. Moreover, evaluation should not only be focused on the microscopic level of the fiber but the performance of the resulting composite materials should be assessed as well. The review also covers research challenges for introducing enzymatic treatment in large scale production as well as inherent limitations and economic aspects. Besides their high selectivity and environmentally-friendly processing conditions, applying enzymes may also result in a less severe mechanical post-treatment implying less fiber damage. Moreover, recycling of enzymes and utilization of byproducts may increase the economic feasibility of the process.