Microbial extraction of chitin from seafood waste using sugars derived from fruit waste-stream

Yun Nian Tan,Wei Ning Chen,Pei Pei Lee

doi:10.1186/s13568-020-0954-7

Abstract

Chitin and chitosan are natural amino polysaccharides that have exceptional biocompatibility in a wide range of applications such as drug delivery carriers, antibacterial agents and food stabilizers. However, conventional chemical extraction methods of chitin from marine waste are costly and hazardous to the environment. Here we report a study where shrimp waste was co-fermented with Lactobacillus plantarum subsp. plantarum ATCC 14917 and Bacillus subtilis subsp. subtilis ATCC 6051 and chitin was successfully extracted after deproteinization and demineralization of the prawn shells. The glucose supplementation for fermentation was replaced by waste substrates to reduce cost and maximize waste utilization. A total of 10 carbon sources were explored, namely sugarcane molasses, light corn syrup, red grape pomace, white grape pomace, apple peel, pineapple peel and core, potato peel, mango peel, banana peel and sweet potato peel. The extracted chitin was chemically characterized by Fourier Transform Infrared Spectroscopy (FTIR) to measure the degree of acetylation, elemental analysis (EA) to measure the carbon/nitrogen ratio and X-ray diffraction (XRD) to measure the degree of crystallinity. A comparison of the quality of the crude extracted chitin was made between the different waste substrates used for fermentation and the experimental results showed that the waste substrates generally make a suitable replacement for glucose in the fermentation process. Red grape pomace resulted in recovery of chitin with a degree of deacetylation of 72.90%, a carbon/nitrogen ratio of 6.85 and a degree of crystallinity of 95.54%. These achieved values were found to be comparable with and even surpassed commercial chitin.

Highlights

The rising affluence of Asia in recent years has ushered an insatiable demand for seafood consumption and heralded a boom in the seafood processing industry worldwide (Yadav et al 2019)
Based on the experimental results obtained, the qualifying criteria for successful extraction of crude chitin from prawn waste at maximum preservation of its native structure was set at a degree of deacetylation above 70%, a carbon/nitrogen ratio above 6.80 and a degree of crystallinity above 90%
These criteria were met by commercial chitin from Sigma Aldrich, as well as when prawn waste was fermented with 20% glucose solution and red grape pomace

Summary

Introduction

The rising affluence of Asia in recent years has ushered an insatiable demand for seafood consumption and heralded a boom in the seafood processing industry worldwide (Yadav et al 2019). 6–8 million tons of crustacean waste are generated annually, as 45–60% of shrimp comprising of head, shell and Chitin, the second most abundant biopolymer in nature after cellulose, is a linear poly-β-(1,4)-N-acetyld-glucosamine occurring in ordered crystalline microfibrils (Al Sagheer et al 2009). It appears in 3 polymorphic forms: α-chitin, β-chitin and γ-chitin (Cardenas et al. Tan et al AMB Expr (2020) 10:17. Β-Chitin, which occurs in squid pens and extracellular fibers of diatoms, is arranged in parallel chains, resulting in less stability with a 70% crystallinity index of chitin fibrils (Alabaraoye et al 2018). Due to the larger distance between neighboring polymer chains, β-chitin is more reactive and dissolves readily (Tripathi and Singh 2018). γ-Chitin, which is rare, is a combination of both α-chitin and β-chitin (Hayes et al 2008)

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