Changes in L-Glutaminase and L-Asparaginase Activities During Vermicomposting of Organic Solid Wastes

Background and Objective: The vermicomposting of solid wastes has attracted much attention during the last decade because animal manure, crop residues and other solid wastes are increasingly cumulating and generating some environmental problems. In this study, L-glutaminase (E.C. 3.5.1.2) and L-asparaginase (E.C. 3.5.1.1) activities were considered as possible tools for the characterization of cow manure (CM) and wheat residue (WR) biodegradation during 60 days of the vermicomposting process. The objectives of this study were to investigate the effects of vermicomposting process on the activity of the amidohydrolases which are effectively involved in N mineralization and subsequent N supply to the plants and to find a bio-indicator reflecting the maturity of the vermicomposts. Materials and Methods: Organic carbon (OC), total nitrogen (TN), L-glutaminase and L-asparaginase activities were determined on seven occasions with 10-day intervals (T0, T10, T20, T30, T40, T50 and T60). Results: The both solid wastes, general decreasing trends in C/N ratio were observed. In contrast, an increasing trend was monitored in the N concentration of the products. Two distinct phases were monitored in L-glutaminase and L-asparaginase activities. During the first phase which last for 30 to 40 days, L-glutaminase was increased in CM and WR by 5.3 and 2.9 fold, respectively. The values for L-asparaginase were 2.3 and 2.5 fold. During the second phase, the enzyme activities decreased slightly or remained unaffected. Conclusion: The enzyme activities were shown to be responding bio-indicators to vermicomposting and thus they can be used as bio-indicators of vermicompost maturity.