Author: Wong, Ai-ling Phoeby
Title: Biopolymers production with carbon source from the wastes of a beer brewery industry
Degree: Ph.D.
Year: 2001
Subject: Biopolymers
Plastics -- Biodegradation
Organic wastes -- Recycling
Hong Kong Polytechnic University -- Dissertations
Department: Department of Applied Biology and Chemical Technology
Pages: xxiii, 270 leaves : ill. (some col.) ; 30 cm
Language: English
Abstract: The main purpose of this study was to assess the potential and feasibility of malt wastes, and other food wastes, such as soy wastes, ice-cream wastes, confectionery wastes, vinegar wastes, milk waste and sesame oil, in the induction of biosynthesis of PHA, in the cellular assembly of novel PHA with improved physical and chemical properties, and in the reduction of the cost of PHA production. In the first part of the experiments, a specific culture of Alcaligenes latus DSM 1124 was selected to ferment several types of food wastes as carbon sources into biopolymers. PHA content was up to 70.1%, and the biomass and PHA density were 32.4 and 22.7 g/L, respectively, when using malt waste as the chief medium and the concentrated sucrose solution as the second stage feeding substrate. Using confectionery wastes as the second stage substrate in the malt waste-based medium also gave a high PHA content (54.1%). In addition, the biopolymer production, by way of using malt waste, of microorganisms from municipal activated sludge was also investigated. The final biomass and polymer concentration were 15.1 and 6.6 g/L dry weight respectively, successfully giving a biopolymer yield a 43.3% of dry weight of the biomass. Furthermore, a specific copolymer of P(3HB-co-3HV) was found to be produced by a mixed culture of activated sludge microorganisms from using soy wastes as nutrients. In the second part, the experiments focused on the synthesis of biopolymer with a higher molecular mass via the bacterial strain, which was selected and isolated from sesame oil, identified as Staphylococcus epidermidis. This strain grew much better under the conditions of temp. 35 C, pH 6.5, Rv 0.2 and C/N 7 of media; however, it was able to produce more polymer under the conditions of temp. 35 C, pH 6.5, Rv 0.2 and C/N 96 of media. Malt waste was a better choice of nutrient source for cell growth and biopolymer accumulation of Staphylococcus epidermidis than other waste sources. The bacterial polymer was characterized by 'H-NMR, 13C-NMR, and FllR. The same biopolymer (PHB) was obtained when different food wastes were used as carbon and energy sources. Molecular weight and molecular weight distribution of PHB were studied by GPC. Molecular weight of PHB produced from various types of food wastes by Alcaligenes latus was higher than using synthetic sucrose medium as nutrient, however, it resulted in the reverse by Staphylococcus epidermidis. Traditional viscosity molecular weight measuring method was improved. One-point method was uncovered for the initial analysis of PHB's molecular weight. In addition, we found that weight average molecular weight (Mw) decreased as fermentation time increased; but the polydispersity (Mw/Mn) increased with a rise in fermentation time in the study on the correlation of fermentation time and molecular weight by Alcaligenes latus. Thermal properties of biopolymers were studied by DSC and TG. Using malt wastes as nutrients by Alcaligenes latus gave a higher melting temperature. Using sucrose, confectionery and sesame oil as nutrients by Staphylococcus epidermidis gave higher melting temperature. Higher thermal decomposition temperature of PHB was obtained in using malt wastes as nutrients both by Alcaligenes latus and Staphylococcus epidermidis. Optimization was carried out for the recovery of microbial PHB from Alcaligenes latus. Results showed that molecular weight can be controlled by changing the hypochlorite concentration, the ratio of chloroform to hypochlorite solution and the extraction time. In addition, the determination of PHB content by thermogravimetric analysis method with wet cell was the first report in our study.
Rights: All rights reserved
Access: open access

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