Green Conversion of Agroindustrial Wastes into Chitin and Chitosan by Rhizopus arrhizus and Cunninghamella elegans Strains

Abstract

This article sets out a method for producing chitin and chitosan by Cunninghamella elegans and Rhizopus arrhizus strains using a green metabolic conversion of agroindustrial wastes (corn steep liquor and molasses). The physicochemical characteristics of the biopolymers and antimicrobial activity are described. Chitin and chitosan were extracted by alkali-acid treatment, and characterized by infrared spectroscopy, viscosity and X-ray diffraction. The effectiveness of chitosan from C. elegans and R. arrhizus in inhibiting the growth of Listeria monocytogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica, Escherichia coli and Yersinia enterocolitica were evaluated by determining the minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC). The highest production of biomass (24.60 g/L), chitin (83.20 mg/g) and chitosan (49.31 mg/g) was obtained by R. arrhizus. Chitin and chitosan from both fungi showed a similar degree of deacetylation, respectively of 25% and 82%, crystallinity indices of 33.80% and 32.80% for chitin, and 20.30% and 17.80% for chitosan. Both chitin and chitosan presented similar viscosimetry of 3.79–3.40 cP and low molecular weight of 5.08 × 103 and 4.68 × 103 g/mol. They both showed identical MIC and MBC for all bacteria assayed. These results suggest that: agricultural wastes can be produced in an environmentally friendly way; chitin and chitosan can be produced economically; and that chitosan has antimicrobial potential against pathogenic bacteria.

Chitosans from Rhizopus stolonifer (strain CBMAI 1551): Characterization and Dense Film Formation

“…Values of 86.1, 85.2 and85.6 % DD were found for A. coerulea, M. rouxii and Rhizopus oryzae, respectively, under submerged cultivation [35]. The easily extracted chitosan from R. arrhizus was determinedto be 86 % DD in a study with agro industrial residues [6]. Fungalchitosans have some distinctive features as absence of allergenic shrimp-related proteins and minerals, among others substances, as stated by Dhillon et al [13] and Kaur &Dhillon [18].…”

“…Many works have focused on identifying alternatives for the traditional methods of chitosan obtainment to overcome the unstable supply due to climate instabilities, absence of quality control during production, but especially in the search of a standardized means of obtainment and processing [2], [6], [18], [22], [31], [32], [36]. Fungi of different groups are interesting options for this purpose, especially with the hope to achieve a standardized product, more appropriated for pharmaceutical and medical purposes [13], [18].…”

Chitinous polymers: extraction from fungal sources, characterization and processing towards value‐added applications

“…These procedures are similar to the ones used for extraction of chitin/chitosan from crustacean shells that also rely on the use of strong alkali for deproteinization. However, a demineralization step employing strong acids is necessary to eliminate inorganic components . Hence the procedures used for fungal sources are simpler and yield less hazardous effluents.…”

“…7,8 Chitin was first isolated from the cell-walls of mushrooms and named 'fungine' in 1823. 9 It is also the main component of crustacean shells as well as the exoskeleton of insects and molluscs, 9,10 which are nowadays the main commercial sources of chitin and chitosan. The demand for these products has been increasing.…”

“…reduction of the polymer's molecular weight (Mw) and degree of acetylation (DA). 9,10 The use of fungi and yeasts, besides not requiring the demineralization step, also enables a more stable and controllable polymer composition, with no seasonal variability or impact of environmental conditions, and the products are free of allergens and heavy metals. [11][12][13] Moreover, besides chitin and chitosan, CGC and ChGC can also be obtained, which adds further value to fungi and yeasts as sources of chitinous polymers.…”