Valorisation of Food Waste and Textile Waste into Value-added Products by Novel Biorefinery Strategies

餐廚廢棄物和紡織廢料轉化為高附加值產品的創新型生物煉製方法研究

Student thesis: Doctoral Thesis

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Award date31 Jul 2017

Abstract

As abundant organic solid waste is generated globally in humans’ daily lives, it has raised increasing research concerns in regard to sustainable waste treatment. Contrary to incineration or landfill that cause serious environmental pollution, biorefinery is proposed as a promising, green and alternative strategy to convert wastes to chemicals, materials and fuels. However, the relatively expensive and complex processing system has impeded its attraction to support large-scale applications; therefore innovative strategies are necessary to realise its full potential. With this perspective, the two research projects reported in this thesis aimed at developing novel biorefinery strategies with improved bioprocessing techniques in solid waste utilisation.

The first project focused on “Bioconversion of Food Waste into Poly(lactic acid) Fibre”. Food waste was applied as a cost-free feedstock for lactic acid production through fungal hydrolysis and bacterial fermentation. In the downstream process, a novel method of lactic acid recovery from the fermentation broth via continuous ultrasonic solvent extraction was developed. Under optimal conditions, lactic acid was recovered with an overall yield of 82 - 84% and purity of 95%. In poly(lactic acid) synthesis, lactide was generated by a newly developed catalytic method using zinc oxide nanoparticle dispersion at yields of over 90% and of high purity, which consequently facilitated a high molecular weight (120,000 - 150,000 g mol-1) of the poly(lactic acid) product.

The second project proposed to recycle textile waste by integration of pretreatment, solid state fermentation, fungal hydrolysis and polyester respinning. In this study, cellulase was harvested in fungal cultivation on textile waste and served as enzyme sources for textile hydrolysis. Various fungal strains were selected and the fermentation environment was optimised in terms of medium, moisture content, supplementary nutrients as well as inoculum size, pH and inducers. The obtained cellulase was of filter paper activity 1.56 FPU g-1 and rich in β-glucosidase (1730 U g-1). It can be applied directly in textile hydrolysis for the recovery of sugar and polyester.

The two projects successfully produced recyclable products from solid wastes through a combination of physical, chemicals and biological conversions. The results from the above studies revealed the high efficiency and feasibility of the novel biorefinery strategies, which also demonstrate the advancement in waste utilisation and contribute to the global target of sustainable development.