Submitted to: Biotechnology Letters
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/10/2005
Publication Date: 2/1/2006
Citation: Solaiman, D., Ashby, R.D., Hotchkiss, A.T., Foglia, T.A. 2006. Biosynthesis of medium-chain-length poly(hydroxyalkanoates) from soy molasses. Biotechnology Letters. 28:157-162. Interpretive Summary: Poly(hydroxyalkanoates) (PHAs) are extra large molecules (polymers) produced by bacteria. They have the properties of plastics, elastomers, and adhesives depending on their compositions. Because of their biodegradability, PHAs are valued as environmentally friendly substitutes for the petrochemically derived polymers. There exists a need to considerably lower the cost of PHA to make it affordable to consumers. One approach to achieve this is to use an inexpensive feedstock in the fermentative production of PHA. Soy molasses (SM) is a coproduct stream generated during the manufacture of soy protein isolates. It has only low-value applications and is thus very inexpensive. In this report, we describe the use of SM as a fermentative feedstock to produce PHA. We first screened several bacteria in the Pseudomonas group to select those capable of growing on the sugars found in SM. Using one of these bacteria, we demonstrated that PHA was indeed produced by this organism when grown on SM. We proceeded to determine the amount and composition of the PHA produced. Although the results showed that the product yield of PHA was low, the composition and thus the properties of the SM-derived polymer were similar to those obtained from more expensive feedstocks. This study thus laid down an important groundwork for future research to use SM to eventually produce PHA in large quantities.
Technical Abstract: Pseudomonas corrugata was selected from a screening process for use in the bioconversion of inexpensive soy molasses into medium-chain-length poly(hydroxyalkanoates) (mcl-PHA). We obtained cell-mass yields of 1.5 g cell-dry-weight (CDW)/l culture with growth medium supplemented with 2% soy molasses, and of an average of 3.4 g CDW/l with 5% soy molasses. Crude PHAs were obtained at 5-17% of CDW. The most prominent repeat-unit monomers in the PHAs were 3-hydroxydodecanoate, 3-hydroxyoctanoate, 3-hydroxydodecanoate, and 3-hydroxytetradecenoate. This work represents the first description of fermentative mcl-PHA production from the soy molasses.