Microbial Conversion of Shrimp Heads to Proteases and Chitin as an Effective Dye Adsorbent

As a green and effective technique in the production of a large number of valuable products, the microbial conversion of chitinous fishery wastes is receiving much attention. In this study, protease production using the Paenibacillus mucilaginosus TKU032 strain was conducted on culture media containing several common types of chitinous fishery by-products serving as the carbon and nitrogen (C/N) nutrition source. Among the chitinous wastes, 1.5% (w/v) shrimp head powder (SHP) was found to be the most appropriate nutritional source for protease production when a maximal enzyme activity of 3.14 ± 0.1 U/mL was observed on the 3rd day of the culture period. The molecular mass of P. mucilaginosus TKU032 protease was estimated to be nearly 32 kDa by the polyacrylamide gel electrophoresis method. The residual SHP obtained from the culture medium was also considered to be utilized for chitin extraction. The deproteinization rate of the fermentation was estimated to be 45%, and the chitin obtained from fermented SHP (fSHP) displayed a similar characteristic Fourier-transform infrared spectroscopy (FTIR) profile as that from SHP. In addition, SHP, fSHP, and chitins obtained from SHP and fSHP were investigated for their adsorptive capacity of nine types of dyes, and chitin obtained from fSHP displayed a good adsorption rate on Congo Red and Red No. 7, at 99% and 97%, respectively. In short, the results provide potential support for the utilization of SHP in the production of P. mucilaginosus TKU032 protease via the fermentation as well as the preparation of chitin from fSHP as an effective dye adsorbent.

Effect of Air Oxidation on Texture, Surface Properties and Dye Adsorption of Wood-Derived Porous Carbon Materials

Hierarchical porous carbon materials made from cork were fabricated using a facile and green method combined with air activation, without any templates and chemical agents. The influence of air activation on the texture and other surface characteristics of the carbon materials were evaluated by various characterization techniques. Results indicate that air oxidation can effectively improve the surface area and the hierarchical porous structure of carbon materials, as well as increase the number of oxygen-containing functional groups on the carbon surface. The specific surface area and the pore volume of the carbon material activated by air at 450 °C (C800-M450) can reach 580 m²/g and 0.379 cm³/g, respectively. These values are considerably higher than those for the non-activated material (C800, 376 m²/g, 0.201 cm³/g). The contents of the functional groups (C-O, C=O and O-H) increased with rising activation temperature. After air activation, the adsorption capacity of the carbon materials for methylene blue (MB) and methyl orange (MO) was increased from 7.7 and 6.4 mg/g for C800 to 312.5 and 97.1 mg/g for C800-M450, respectively. The excellent dye removal of the materials suggests that the porous carbon obtained from biomass can be potentially used for wastewater treatment.