Innovation and Technology Commission
Valorisation of food waste for sustainable production of chemicals, materials and fuels Daniel Pleissner, Sanjib Kumar Karmee, Wan Chi Lam, Haque Md Ariful, Yunzi Hu, Rick Arancon, Tsz Him Kwan, Kin Yan Lau, Carol Sze Ki Lin School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong Background: Between 12 and 39% of municipal solid waste is food based and this causes environmental, social and economic problems. High contents of starch and proteins, however, make food waste a potentially valuable source of the glucose and free amino nitrogen needed in most biotechnological processes for production of chemicals, materials and fuels. Our research focuses on the development of approaches for the valorisation of food waste in biotechnological and chemical processes. The recovery of carbon and nitrogen from food waste by biological methods enables the recycling of valuable nutrients for the production of chemicals, materials and fuels. Valorisation of food waste is not only an environmentally benign waste treatment, but it also benefits to the bio-based economy, as pure and expensive nutrient sources can be substituted. The integration of food waste treatment in existing biotechnological processes can shorten the pathway from “no value waste” to “value-added products”. Together with green chemistry technologies, it contributes to a sustainable society.1 Direct conversion of food waste into high-value products
Food waste hydrolysate as feedstock in microbial fermentation
Monascorubramine
Monascus purpureus
Rubropunctamine
Monascus red pigments
Succinic acid
Fermentation
Red Monascus pigments (e.g. Monascorubramine or rubropunctamine) are commonly used as food coloring agents which are produced through fermentation using glucose as carbon source. To develop a cost efficient strategy for red pigments production, the feasibility of using bakery waste as substrate is under investigation. Bakery waste suspension was used for fermentation with Monascus purpureus at 30°C for 9 days. Production of red pigment was estimated by measuring the absorbance at 500 nm of the fermented broth. Preliminary results show that maximum amount of red pigment is produced at Day 8 with absorbance value of 2.5 highlighting the feasibility of the approach. Optimization of fermentation conditions to increase pigment production is undergoing.
Bakery waste from Starbucks Hong Kong was evaluated for the potential of succinic acid production. Cake and pastry hydrolysates produced via simultaneous hydrolysis and fungal autolysis were used separately as feedstock in Actinobacillus succinogenes fermentation. A cationexchange resin-based recovery process (via vacuum distillation and crystallisation) was used subsequently to recover the succinic acid crystals from fermentation broth. Succinic acid crystals with purity of 97% was obtained. Results of the present work successfully demonstrated the novel use of bakery waste as the generic fermentation feedstock for the sustainable production of succinic acid as platform chemical in food waste-based biorefinery.3,4
Actinobacillus succinogenes
Food waste Alpha-linolenic acid (ALA, omega-3)
Fatty acid extraction and transesterification TLC of reaction mixture
Biodiesel
Chlorella pyrenoidosa
The remaining solid obtained after fungal hydrolysis of food waste was subjected to transesterification with methanol under microwaves. Both Ca(OH)2 and Mg(OH)2 were used as catalysts for this transesterification reaction. Reactions were carried out for 30 minutes at 100°C. Qualitative analysis of the reaction mixtures by thin layer chromatography reveal the formation of biodiesel. Analysis by GC and 1H NMR will be carried out for the quantification of biodiesel. Currently, work is under progress to find out suitable reaction conditions for high yield of biodiesel.
Hydrolysate obtained by fungal hydrolysis of food waste is investigated for its suitability as a cost-efficient nutrient source in microalgae cultivations. The heterotrophic microalga Chlorella pyrenoidosa was found to grow well on pure food waste hydrolysate and algal biomass rich in particularly polyunsaturated fatty acids has been obtained.5
Aspergillus awamori Multienzyme solution Production of multienzyme solution using bakery waste as sole substrate via solid state fermentation was evaluated using A. awamori and A. oryzae. Glucoamylase and protease were extracted from bakery waste simply with water. Glucoamylase (76.1 ± 6.1 U/mL) and protease (274.7 ± 4.7 U/mL) were detected in the enzyme extracts after fermentation with A. awamori and A. oryzae, respectively. Multienzyme solution is formed after mixing the two extracts and results show that the multienzyme solution can be used to hydrolyze restaurant food waste releasing a glucose and amino acids rich solution as fermentation feedstock for chemicals production. Results from this work provide an alternative strategy for waste management and sustainable production of glucose and amino acids applicable in many biotechnological processes.2
Solid state fermentation
Aspergillus oryzae
Polyhydroxybutyrate (PHB, bio-plastic) Halomonas boliviensis
Biodegradable plastics produced from waste would be an alternative to petroleum-derived plastics. This work focuses on the utilisation of bakery waste for the production of polyhydroxybutyrate (PHB) which is a family of biodegradable plastics that is accumulated intracellularly by many bacteria. The feasibility of PHB production by Halomonas boliviensis from bakery waste, followed by PHB recovery and industrial scale process simulation were studied. Results showed that H. boliviensis was able to accumulate PHB using bakery waste. PHB solid was recovered by solvent extraction. References with further information: 1. Pleissner D, Lin CSK. 2013. Valorisation of food waste in biotechnological processes. Sustainable Chemical Processes 1:21, DOI 10.1186/2043-7129-1-21 2. Lam WC, Pleissner D, Lin CSK. 2013. Production of fungal glucoamylase for glucose production from food waste. Biomolecules, 3, 651-661, DOI 10.3390/biom3030651 3. Zhang AYZ, Sun Z, Leung CCJ, Han W, Lau KY, Li M, Lin CSK, 2013. Valorisation of bakery waste for succinic acid production. Green Chemistry, 15, 690-695 4. Leung CCJ, Cheung ASY, Zhang AYZ, Lam KF, Lin CSK, 2012. Utilisation of waste bread for fermentative succinic acid production. Biochemical Engineering Journal, 65, 10-15 5. Pleissner D, Lam WC, Sun Z, Lin CSK. 2013. Food waste as nutrient source in heterotrophic microalgae cultivation. Bioresource Technology, 137, 139-146
The authors acknowledge the Biomass funding from the Ability R&D Energy Research Centre (AERC) at the School of Energy and Environment in the City University of Hong Kong. We are also grateful to the donation from the Coffee Concept (Hong Kong) Ltd. for the ‘Care for Our Planet’ campaign, as well as a grant from the City University of Hong Kong (Project No. 7200248). Authors acknowledge the Innovation and Technology Fund from the Innovation and Technology Commission (ITS/353/11 and ITS/353/12) in Hong Kong.
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20th Anniversary Workshop on ‘’Environmental Science and Technology for Sustainable Development”, The Chinese University of Hong Kong, Hong Kong 25 January 2014
