Abstract
A huge amount of food waste is generated worldwide every day which exerts an enormous negative impact on the environment. Traditional waste management techniques and recycling of the unutilized nutrients for value-added products have paved the way for food waste recycling and nutrient management. In the first project, a concept of utilizing food waste as a nutrient source for the fermentative production of bio-colourant by Monasucus purpureus has been developed. The proposed ideas provide an innovative approach to establish a system or method to reduce the food waste problem encountered by Hong Kong and other countries. Food waste collected from bakery stores was used in submerged and solid-state fermentation of Monascus purpureus to produce bio-colourant, which could potentially be applied in food and textile industries. The feasibility of utilizing bakery waste hydrolysate derived from hydrolytic reactions by Aspergillus awamori and Aspergillus oryzae for fermentative pigment production was investigated. Preliminary data from food waste hydrolysate experiments indicated that the highest pigment yield (about 24 AU/g glucose) was obtained with food waste hydrolysate containing 5 g/L initial glucose. Results from the solid state fermentation studies indicated that the highest activity of glucoamylase and protease achieved was 8 U/g and 117 U/g respectively, at an initial moisture content of 55% and 65% respectively at a 30 °C incubation temperature.The outcome of this study demonstrated that Monascus purpureus constitutes a promising host for bio-colourant and enzyme production using recovered sugars and amino acids from bakery waste.
In the second project, food and beverage wastes were treated by a biotransformation process as a new approach for production of fructose as a high value-added product. From the compositional analysis of food and beverage wastes, it was found that food and beverage wastes initially contain a significant amount of glucose (30-40 g/L in beverages and 80-140 g/L in packaged food waste), fructose (around 40-42 g/L in beverages and 5-10 g/L in food wastes) and sucrose (especially Tropicana juices and around 25 g/L and 10-15 g/L in Quaker cereals). The optimized conditions of pectinase and sucrase were found to be a temperature of 50 °C and pH of 4 – 4.5 (which is the natural pH of beverages); thus they could be dosed simultaneously to produce fructose and remove pectin from beverage waste. An activated carbon column could remove the colorants with more than 95% sugar recovery, and ion exchange resin treatment could remove more than 98% of ions. Finally, ligand exchange chromatography could separate fructose from glucose effectively; 768 mL fructose-rich stream with 80.8% fructose could be produced from 400 mL mixed beverage waste, resulting in a fructose recovery efficiency of 78.9%. Study of bakery waste revealed a starch recovery of 94.3% (after hydrolysis) and ion removal of over 98% (after ion exchange chromatography) from the waste hydrolysate stream. Around 28.3% of fructose recovered from the glucose-fructose rich stream and the bioconversion process exhibited a total sugar recovery of 68.9%. Results from the carbohydraterich Quaker cereals study reveal that it contains over 60% and about 55% carbohydrate and starch respectively. Ion removal studies of the carbohydrate-rich stream exhibited a 98% separation and the final separation efficiency and recovery of fructose from this waste stream attained 82.4 and 67.7% respectively.
Overall, fructose derived from bioconversion of food and beverage waste streams can be promising candidates for further transformation. Thus this study reflects a bio-base development of value-added products and a feasible approach for food waste problem mitigation for a sustainable environment.
| Date of Award | 30 Aug 2016 |
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| Original language | English |
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| Supervisor | Sze Ki Carol LIN (Supervisor) |