Comparison between solid and liquid acids for production of low molecular weight chitosan using systematic DOE-based approach
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Chitosan is an abundantly available biodegradable polymer with diverse applications in various chemical and biomedical industries. However, it has remained underutilized due to its bulky and intractable nature, limiting its application in various fields. The major drawback, however, is poor aqueous solubility and thus preparation of low molecular weight derivatives of chitosan (LMWC) is an ideal solution to overcome the drawbacks associated with the parent polymer. The present study reports a sustainable method to produce LMWC, using H-β Zeolite as a green catalyst in comparison to the traditional depolymerization methods, based on nitrous acid. Successful decrease in molecular weight from 1157 to 175 kDa was achieved as studied by gel permeation chromatography. Furthermore, spray drying assisted in achieving uniform sized particles of LMWC of size less than 100 µm. Integration of response surface methodology for process optimization led to the negligible formation of by-products like 5-hydroxymethylfurfural. Comparative investigations confirmed the consistency of the developed method, simultaneously presenting additional advantages such as catalyst reusability, process reproducibility and process safety. Our findings demonstrate a greener approach for preparation of consistent quality LMWC, by implementing systemic stratagem of design of experiments.
KeywordsChitosan H-β Zeolite Solid acid catalysis Response surface methodology Low molecular weight chitosan
The authors are thankful to University Grants Commission for the UGC-SAP fellowship [F.25-1/2014-15 (BSR)/No. F.8-10/2007(BSR)] and [F.4-1/2006 (BSR)/8-10/2007(BSR)] for financial support. The authors would like to acknowledge DST-Nanomission (Sanction No. SR/NM/NS-1145/2012) for the zetasizer instrument and DST-FIST (Sanction No. SR/FST/ETII-058/2013 (C)) for Gel Permeation Chromatography. The authors are also very thankful to Nano-xpert technologies for technical support and providing gift sample of solid acid. Special thanks to Tejal Pant and Manish Gore for assistance in drafting the manuscript.