Enzymatic Synthesis of 100% Lignin Biobased Granules as Fertilizer Storage and Controlled Slow Release Systems

In an attempt to reduce the loss of fertilizer due to leaching, this study investigates for the first time the possibility of synthesizing lignosulfonate-based fertilizer slow release granules by using laccases as green catalysts. Trametes hirsuta laccases (THL) extensively oxidized and polymerized lignosulfonates resulting in 62 and 54% decrease in phenolic groups from 52 g l–1 in samples incubated at pH 6 and 7, respectively, and as evidenced by the formation insoluble polymers at pH 6 and 7 in less than 2 h. Preliminary attempts to synthesize 100% lignosulfonate granules resulted in highly brittle randomly breaking particles with most particles <0.5 mm in diameter when dried. In order to produce bigger and regular sized lignosulfonate granules, 1% w/w alginate was incorporated into the polymerized lignosulfonates resulting in perfectly stable granules. Release studies showed that 100% lignosulfonate-based granules released all of the potassium nitrate and potassium phosphate in <5 days. However, in addition to helping make perfect granules, the incorporation of 1% alginate allowed the prolonged release of fertilizer over 25 days. This study therefore shows for the first time the possibility of synthesizing 100% biodegradable fertilizer delivery systems using 100% green technology “enzymes”.