Production of Polyhydroxyalkanoates by Azotobacter vinelandii UWD Using Swine Wastewater: Effect of Supplementing Glucose, Yeast Extract, and Inorganic Salts

• Published in: Biotechnology and bioprocess engineering Vol. 13; no. 6; pp. 651 - 658
• Main Authors: Ryu, H.W. (Soongsil University, Seoul, Republic of Korea), Cho, K.S. (Ewha Womans University, Seoul, Republic of Korea), Goodrich, Philip R. (University of Minnesota, MN, USA), Park, C.H. (Kyung Hee University, Yongin, Republic of Korea), E-mail: chpark@khu.ac.kr
• Format: Journal Article
• Language: English
• Published: Heidelberg The Korean Society for Biotechnology and Bioengineering 01.12.2008; Springer Nature B.V; 한국생물공학회
• Subjects: Animal wastes; AZOTOBACTER VINELANDII; Bacteria; Biodegradation; Bioplastics; Biotechnology; Carbon; Cell growth; Chemistry; Chemistry and Materials Science; Engineering; Environmental impact; GLUCOSA; GLUCOSE; Industrial and Production Engineering; Industrial wastes; Nitrogen; Nutrients; Organic wastes; Plastics; Polyhydroxyalkanoates; Raw materials; Salts; Studies; Swine houses; swine wastewater; Yeast; Yeasts; 생물공학; Azotobacter vinelandii
• ISSN: 1226-8372; 1976-3816
• DOI: 10.1007/s12257-008-0072-x

This study examined the effect of adding glucose, yeast extract, and inorganic salts to swine wastewater (SWW) in a batch culture on the production of a biodegradable plastic, polyhydroxyalkanoate (PHA). A bacterial strain, Azotobacter vinelandii UWD, was used to produce PHA without limiting the non-carbon nutrients. The addition of glucose (30 g/L) to the SWW medium increased the level of cell growth (4.4~7.0 times) and PHA production (3.8~8.5 times) depending upon the dilution of SWW. A 50% dilution of SWW was found to be optimal considering the dry cell weight (9.40 g/L), PHA content (58 wt%), and hydroxyvalerate (HV) mol fraction in the PHA (4.3 mol%). A 75% SWW medium was more advantageous for producing PHA with a higher HV fraction (7.1 mol%) at the expense of losing 22% of PHA production. The undiluted SWW medium produced less than one third of the PHA compared with the 50% SWW medium, but the HV fraction was the highest (10.8 mol%). Regarding the effect of the glucose concentration, at 20 g/L glucose, the dry cell weight and level of PHA production increased to 9.34 g/L (0.63 g PHA/g dry cell weight) and 5.90 g/L, respectively. At 50 g/L glucose, there was no significant increase in PHA production. For the glucose-supplemented (30 g/L) 50% SWW medium, the addition of a nitrogen source (1 g/L of yeast extract) did not increase the level of cell growth or PHA production because the C:N ratio (23:1) was already close to the optimal value (22:1). Better aeration increased the productivity of PHA. External nitrogen supplements (1 g/L of yeast extract) and other essential mineral salts was not necessary for bacterial growth because they were contained in the SM. These results suggest that SWW is an excellent feedstock for producing larger amounts of the value-added material, PHA, if it is combined with carbohydrate-rich organic waste.