Chitosan production with larval exoskeletons derived from the insect protein production
This work provides methods for chitosan production with larval exoskeletons from Hermetia illucens and characterizes the produced material. The study aims to provide optimal reaction conditions for the purification of chitin from insect material and evaluates the key characteristics of the insect-based chitosan compared to crab shell chitosan. H. illucens is a sustainable source of high-quality protein, lipids and compost currently applied as aquaculture feed and soil improver. The ecdysis of the H. illucens larvae results in larval exoskeletons (LE) rich in chitin and suitable for chitosan production. Using procedures based on crab shell processing, two steps were performed to purify chitin from the larval exoskeletons. The results showed that formic acid is a suitable demineralization agent, requiring 5 mol per kg larval exoskeletons and thorough washing afterwards for 89 % demineralization effectivity (DME). The effect of the deproteinization variables were explored via design of experiments and analyzed using linear regression resulting in chitin contents of the deproteinized material of 83 % in small-scale and 87 % in 10 L-scale, respectively. Heterogeneous and homogeneous deacetylation was performed to convert chitin in different chitosan fractions. Heterogeneous deacetylation at 120 °C resulted in a deacetylation degree (DD) of 72 % and a yield of 43 % at maximum with regard to the total chitin applied. Homogeneous deacetylation at 4 °C resulted in a low chitosan yield of 13 % and a DD of 34 %. However, chitosan solubilized in acetic acid revealed superior film forming properties and a high viscosity. The results indicated that the chitosan from insects has comparable properties than those produced from crab shells, although the properties are also strongly dependent on the manufacturing conditions.