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Hui Li [1] and Suping Zhou [1] and Terrance Johnson [1] and Koen Vercruysse [1] and Ouyang Lizhi [1] and Parthasarathy Ranganathan [1] and Nsoki Phambu [1] and Alexander J. Ropelewski [2] and Theodore W. Thannhauser [3]

Academic Editor: Raffaele Cucciniello

1, College of Agricultural, Human and Natural Sciences, Tennessee State University, Nashville, TN, USA, tnstate.edu

2, Pittsburgh Supercomputing Center, Pittsburgh, PA, USA, psc.edu

3, R.W. Holley Center for Agriculture and Health, Plant, Soil and Nutrition Research Unit, USDA, ARS, Ithaca, NY, USA, usda.gov

Received Apr 11, 2017; Accepted Jul 9, 2017

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction

Since 1960s, driven by public concerns about environmental pollution by petroleum-derived plastics [1–6] and the escalating crude oil price due to the depletion of fossil oil resources, bioplastics have attracted widespread attention, as eco-friendly, biodegradable, and sustainable alternatives [4, 7]. Among all the biodegradable plastics, the polyhydroxyalkanoates (PHAs) family has unique properties like insolubility in water, biocompatibility, oxygen permeability, and ultraviolet (UV) resistance [8]. Because of these advantageous characteristics, comprehensive applications have been discovered and developed using PHAs-derived materials for packaging plastics, medical materials, chiral monomer, and others [9, 10]. Also stable engineered industrial microbial strains have been developed overexpressing genes in PHAs biosynthesis pathway with additional functions in regulating cellular metabolisms and stress resistance [11, 12]. The main member of the PHAs family is polyhydroxybutyrate (PHB). These polymers are accumulated intracellularly in PHB producing bacteria when cultured under carbon-excess and other nutrients-limited conditions [13].

A large number of microorganisms have been found to accumulate PHA as lipoidic storage materials in the cytosol [14–17]. These microorganisms are mainly divided into four classes (I, II, III, and IV) based on the type of PHA synthases, which are the key enzymes for PHA biosynthesis [18]. While a single subunit PhaC was found in class I (e.g., Ralstonia eutropha) and class II (e.g., Pseudomonas aeruginosa) synthases, two subunits, PhaE and PhaC, or PhaR and PhaC, were suggested to be used, respectively, in type III (e.g., Allochromatium vinosum) and type IV (e.g., Bacillus megaterium) synthases [19, 20]. Classes I, III, and...

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