Production of chitosan from Aspergillus niger and quantitative evaluation of the process using adapted analytical tools

The chitosan production process from fishery waste is already established in industrial scale, whereby fungal chitosan is produced in lower amounts. Since fungal chitosan could be isolated from under-valorized vegan streams while exhibiting slightly different characteristics, it has also potential for other applications. Within this publication, we focus on the chitosan production from Aspergillus niger. This study provides a detailed determination of the biomass composition, adapting and comparing different analytical tools, with special focus on the chitin and chitosan content. The major content of the dried biomass is composed of glucans (48.6 ± 1.4%), followed by proteins with an amount of 22.2 ± 0.7%. Chitin and chitosan provide 16.0 ± 0.8% of the biomass. Within our chitosan production studies, we compared the effect of different process strategies including steps as deproteinization (DP), acid extraction (AE), deacetylation (DA), as well as purification. Initially, we obtained poor values (lower than 73.6%) for the chitosan purity. A direct DA step followed by purification resulted in a chitosan purity of up to 89.6%, a recovery of 30.5% and a yield with regard to the biomass of 5.5%. The DA degree of the resulting chitosan is similar to chitosan derived from fishery waste, whereas the molecular weight is lower. The results achieved so far are consistent with the literature, extending beyond, the data emphasized that a chitosan production from residual fungal biomass after fermentation is suitable by direct DA and purification. However, further adaption is necessary so that other matrix compounds could be also obtained.