Production of Chitosanase by Lentzea sp. OUR-I1 Using Acid-Pretreated Shrimp Shell in an Air-Lift Bioreactor and the Feasibility of Utilizing the Residual Biomass

Chitosanase is an attractive enzymatic tool for the production of bioactive chitooligosaccharides. Nevertheless, its industrial use is restricted by its high cost and insufficient availability because chitosanase production needs an expensive inducer, chitosan. Therefore, this study developed a process to produce chitosanase from abundant and inexpensive shrimp shell waste entailing the pretreatment of shrimp shell powder (SSP) with 0.4 M acetic acid (AcSSP), which increased the substrate bioavailability and enhanced the chitosanase production by Lentzea sp. OUR-I1 four-fold. The initial flask-based process was scaled up into an air-lift bioreactor (ALB) and the maximum chitosanase activity (0.974 U/mL) was observed at an aeration rate of 2.0 vvm. This is the first report indicating the suitability of ALB for chitosanase production by Lentzea sp. OUR-I1. Interestingly, Lentzea sp. OUR-I1 also produces a yellow pigment with prospective structure as carotenoids, indicating that the mycelium could be reused in the production of pigments. In addition, the fermented AcSPP displayed the FTIR spectrum of chitin and has high potential as an absorbent for methyl orange, methylene blue and coomassie brilliant blue, with a maximum decolorization efficiency of 73.21, 64.59 and 87.93%, respectively. The process developed represents a cost effective and environmentally friendly method of valorizing a waste product from the food industry into valuable bioproducts. Graphic Abstract