Submitted to: Polymers and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2008
Publication Date: 10/1/2008
Publication URL: http://dx.doi.org/10.1007/s10924-008-0108-5
Citation: Ashby, R.D., Solaiman, D.K.Y. 2008. Poly(hydroxyalkanoate) Biosynthesis from Crude Alaskan Pollock (Theragra chalcogramma) Oil. Polymers and the Environment. 16:221-229. Interpretive Summary: The Alaskan fishing industry produces approximately two-thirds of the total wild fish consumed by humans in the United States. However, since only a fraction of each fish is actually eaten, a large portion (including the viscera, heads, skin, etc.) remains as a byproduct of the industry. Between the years 2000 and 2004 the average amount of fish byproducts generated from the major fish species harvested in Alaska (including Walleye Pollock, Salmon, and Cod) were in excess of 1 million metric tons per year. Some of this material was processed into fish oil and fish protein, important dietary ingredients. However, because of high processing costs, much of this material was deemed unusable and returned to the sea. In order to confer increased value to this high volume, low-value byproduct, fish oil from Walleye Pollock was used as a bacterial growth substrate for the synthesis of biobased bacterial polyesters called poly(hydroxyalkanoates) (PHAs). By varying the specific bacterial strain, different types of PHA polymers were produced with widely diverse properties. Two bacterial strains produced a polymer termed poly-3-hydroxybutyrate (PHB), which is known to exhibit properties equivalent to some of the common petrochemical-based polymers such as polyethylene (PE) and polypropylene (PP). In contrast, four of the bacterial strains surveyed produced what are termed medium-chain-length PHA (mcl-PHA) polymers with tacky, elastomeric character. The ability to produce biodegradable polymers that have already attracted industrial interest with widely divergent properties from the oil derived from the byproducts of the Alaskan fishing industry will potentially create a new outlet for this material and could result in adding value to the byproduct stream, thus helping to generate additional revenue for the Alaskan fishing industry.
Technical Abstract: Six strains of Pseudomonas were tested for their abilities to synthesize poly(hydroxyalkanoate) (PHA) polymers from crude Pollock oil, a large volume byproduct of the Alaskan fishing industry. All six strains were found to produce PHA polymers from hydrolyzed Pollock oil with productivities (P; the percent of the cell mass that is polymer) ranging from 6% to 53% of the cell dry weight (CDW). Two strains, P. oleovorans NRRL B-778 (P = 27%) and P. oleovorans NRRL B-14682 (P = 6%), synthesized poly(3-hydroxybutyrate) (PHB). Four strains, P. oleovorans NRRL B-14683 (P = 52%), P. resinovorans NRRL B-2649 (P = 53%), P. corrugata 388 (P = 43%), and P. putida KT2442 (P = 39%), synthesized medium-chain-length PHA (mcl-PHA) polymers. All mcl-PHA polymers were primarily composed of 3-hydroxyoctanoic acid (C8:0) and 3-hydroxydecanoic acid (C10:0) amounting to at least 75% of the total monomers present. Unsaturated monomers were also present in the mcl-PHA polymers at concentrations between 13% and 16%, providing loci for polymer derivatization and/or crosslinking.