Abstract
Mucor circinelloides is a fungus that has been reported to produce ethanol, oil, protein, phosphate and glucosamine, depending on the available nutrients and cultivation conditions. Due to its ability to produce extracellular proteases, it is able to ferment polypeptides and amino acids broken down from various protein sources. In this study, we attempted to culture the Mucor circinelloides on waste substrates to deproteinize prawn shells for the extraction of chitin and subsequently extract chitosan from its fungal cell wall in a concurrent fermentation. The physio-chemical properties of the extracted crustacean chitin and fungal chitosan were determined by Fourier Transform Infrared Spectroscopy (FTIR) and Elemental Analysis (EA). We found that Mucor circinelloides grown on okara and coffee waste behaved as an excellent protease producer and successfully extracted chitin from prawn shells with a degree of deacetylation of 69.94% and 68.82%, respectively, comparable to commercial chitin (70.46%). The fungal chitosan extracted from the fermentation of Mucor circinelloides on red grape pomace substrate showed a degree of deacetylation of 61.05%, comparable to commercial chitosan (64.00%). Our results suggested feasibility of extracting chitosan from seafood waste-streams using cost-effective microbial fermentation.
Highlights
Chitin (β-(1-4)-poly-N-acetyl-d-glucosamine), the second most abundant polysaccharide occurring in nature after cellulose, is found in the exoskeletons of crustaceans, such as crayfish, crabs and shrimps, as well as in the cell walls of fungi, such as mushrooms [1]
We explore a variety of waste substrates for the simultaneous production of chitin from prawn shells and cultivation of fungal chitosan from Mucor circinelloides by placing prawn shell waste in direct contact with the fermentation of filamentous fungi
Cultivated fungal chitosan demineralized by Lactobacillus plantarum and deproteinized by Bacillus subtilis ranged from 0.5 g to 1 g, which translated to an average yield of 5% to 10% per gram of biomass waste substrate used
Summary
Chitin (β-(1-4)-poly-N-acetyl-d-glucosamine), the second most abundant polysaccharide occurring in nature after cellulose, is found in the exoskeletons of crustaceans, such as crayfish, crabs and shrimps, as well as in the cell walls of fungi, such as mushrooms [1]. Due to its high biocompatibility, predictable biodegradability, anti-microbial activity and non-toxicity to cells, chitin and its deacetylated derivative chitosan have been deployed in a wide range of emerging biomedical applications [2]. While α-chitin is made up of two N-N’-diacetyl-glucosamine units forming two polymer chains in an anti-parallel and stable arrangement, β-chitin enjoys a more flexible structure composed of only one poly-N-acetylglucosamine unit arranged in parallel polymer chains with no inter-sheet H bonds [5]. Varying degrees of deacetylation have been reported in both crustaceans and fungi, with a continuum of structure between fully acetylated chitin and fully deacetylated chitosan [7]
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