Production of antimicrobial bio-composite films from citrus waste by fungi

Annually around 15 million tons of citrus waste is produced by juice production industry. This project aims to develop methods for production of bio-composite materials from citrus wastes.

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Different strains of zygomycetes fungi will be employed to produce new antimicrobial bio-composite films from citrus wastes from e.g. Borås Brämhults Juice AB. Zygomycetes fungi are well known for being safe for humans and are used in fermented food such as “tempe” in Southeast Asia. Additionally, being able to grow on a variety of metabolites as well as production of a wide range of products including ethanol, lactic acid, enzymes, and products derived from biomass, e.g. chitosan, makes them an interesting choice for industrial applications. Citrus wastes are rich in pectin, glucan and hemicellulose.

In this project the glucan and hemicellulose fractions will be fermented using zygomycetes fungi to produce the fungal biomass. The cultivation condition will be optimized in order to get the highest levels of chitosan in the fungal biomass. Fungal chitosan will be extracted from the cell wall of the obtained biomass. This will be used together with the remaining pectin of citrus waste for production of the bio-composite films that can be used as edible coatings to extend the shelf life of different food products. A casting method will be developed for preparations of fungal chitosan-pectin films and preparation conditions will be optimized to meet the requirements for food packaging industry. Antimicrobial and mechanical properties as well as the resistance for the films towards transfer of water vapour, oxygen and carbon dioxide will be optimized.

  1. Optimization of fungal growing conditions on citrus waste to achieve the highest chitosan yield.
  2. Development for new methods for simultaneous cultivation of fungi on citrus waste and pectin recovery.
  3. Recovery and purification of chitosan from cultivated biomass.
  4. Development of fungal chitosan-pectin films suitable for packaging purposes

The Swedish Centre for Resource Recovery at the University of Borås has many years of experience of converting the citrus to different value added products e.g. ethanol, biogas and pectin.