Production of Chitin from Penaeus vannamei By-Products to Pilot Plant Scale Using a Combination of Enzymatic and Chemical Processes and Subsequent Optimization of the Chemical Production of Chitosan by Response Surface Methodology

Abstract

The waste generated from shrimp processing contains valuable materials such as protein, carotenoids, and chitin. The present study describes a process at pilot plant scale to recover chitin from the cephalothorax of Penaeus vannamei using mild conditions. The application of a sequential enzymatic-acid-alkaline treatment yields 30% chitin of comparable purity to commercial sources. Effluents from the process are rich in protein and astaxanthin, and represent inputs for further by-product recovery. As a last step, chitin is deacetylated to produce chitosan; the optimal conditions are established by applying a response surface methodology (RSM). Under these conditions, deacetylation reaches 92% as determined by Proton Nuclear Magnetic Resonance (¹H-NMR), and the molecular weight (Mw) of chitosan is estimated at 82 KDa by gel permeation chromatography (GPC). Chitin and chitosan microstructures are characterized by Scanning Electron Microscopy (SEM).

Keywords: Penaeus vannamei shells; by-products valorization; chitin; chitosan; response surface methodology.

Figure 1

Photograph of the pilot plan developed for the present study (A); Flowchart of chitin production at pilot plan scale combining enzymatic and chemical steps (B).

Figure 1

Photograph of the pilot plan developed for the present study (A); Flowchart of chitin production at pilot plan scale combining enzymatic and chemical steps (B).

Figure 2

Infrared (IR) spectrum of chitin pattern provided by Sigma-Aldrich (A); IR spectrum of chitin from P. vannamei by-products (B).

Figure 3

Image of SEM of chitin (A) and normal pictures of white flakes of purified chitin (B).

Figure 4

¹H-NMR spectra for chitosan with high DD obtained in the experimental condition t = 24 h/NaOH = 50% (left) and low DD obtained in the experimental condition t = 20.6 h/NaOH = 35.9% (right). GlcNAc: N-acetylglucosamine, GlcN: glucosamine, NAc: N-acetyl.

Figure 5

Experimental data (points) and theoretical response surfaces describing the joint effects of alkali and processing time on chitosan production from P. vannamei chitin.

Figure 6

Images of SEM for chitin (A,B) and chitosan (C,D) samples obtained at different experimental conditions. (A) 12.5 h/NaOH 30%; (B) 20.6 h/NaOH 35.9%; (C) 12.5 h/NaOH 50% and (D) 24 h/NaOH 50%.