Towards the production of a novel biologically produced thermoelastomer from cane molasses

Abstract

The production of microbial biopolymers has drawn the attention of the scientific community due to the use of raw materials from renewable sources, providing an alternative to oil-based plastics. The polyhydroxyalkanoates (PHAs) are a family of polymers synthesized as carbon and energy reserve by several microbial groups that are potential substitutes to conventional plastics. Their commercialization, however, is still limited due to the high production costs, when compared to their non-renewable competitors. To overcome this barrier, new research is required to enable the use of inexpensive raw materials and develop novel, more efficient technologies for biotechnological production of PHA. Additionally, the inclusion of the production of biopolymers within a biorefinery is very advantageous for its commercial viability due to the existence of an already consolidated infrastructure and the availability of energy and other inputs. The integration of PHA production with a sugar and ethanol biorefinery provides great operational flexibility, allowing adjustments of the raw material flow according to seasonal fluctuations and market demands. In this context, this research project aims at the production of medium-chain-length PHAs (mcl-PHAs) from sugar cane molasses, a by-product of sugar refining. As opposed to short-chain-length PHAs (scl-PHAs), mcl-PHAs have high value-added applications due to its thermoelastomeric properties. We propose to employ the mcl-PHA-accumulating bacterial strain Pseudomonas putida KT2440 in carbon-limited fed-batch reactors capable of achieving high biomass concentrations, in a setting similar to that used in commercial-scale applications. Different feeding strategies will be evaluated in order to obtain high yield, high-quality mcl-PHA using sucrose, which is the main carbon substrate in sugar cane molasses. Once the process is optimized, PHA production from enzimatically treated molasses will be assessed. The productivity of highly efficient recombinant strains of P. putida will also be evaluated. The proposed approach is an essential step in the development of a cost-effective process to produce a new family of high-quality compostable thermoelastomers from sugar cane molasses.