Cell-wall degrading enzymes in slow filters of closed hydroponic systems

摘要

Slow filtration is an effective, reliable and economically reasonable technique for dismfestation of nutrient solution in closed irrigation systems. However, the problematic control of its efficacy is a major shortcoming of this technique. The efficacy of slow filters against pathogenic microorganisms is caused by a complex combination of mechanical, physical-chemical and biological factors. Due to the importance of biological factors, parameters describing biological processes are possible factors for predicting the efficacy of slow filters. The natural occurrence, induction and significance of cell wall-degrading enzymes (CWDE, such as protease, chitinase, cellulase and (β-1,3-glucanase) in slow niters were investigated. On non-treated slow filters of rockwool, proteolytic and chitinolytic activity was enhanced mainly in the top filter layer compared with the nutrient solution. For cellulase and (β-1,3-glucanase activity, no accumulation could be found. Induction of all CWDE was possible in situ with a preparation of Fusarium oxysporum f. sp. cyclaminis. Statistical analysis revealed that enzyme activity on rockwool was correlated with the efficacy of slow filters (r~2 = 0.495). Chitinase had the strongest influence, followed by protease and cellulase, whereas (β-l,3-glucanase had no significance. Hence, enzyme activity represents one parameter for predicting the prevailing efficacy of slow filters.