Polyhydroxyalkanoates production by engineered Cupriavidus necator from waste material containing lactose

Area of Science:

• Microbial Biotechnology
• Synthetic Biology
• Biopolymer Production

Background:

• Cupriavidus necator is a known producer of polyhydroxyalkanoates (PHAs).
• The wild-type strain cannot metabolize lactose, limiting its use with lactose-rich feedstocks like cheese whey.
• PHA intracellular degradation can reduce overall yields.

Purpose of the Study:

• To engineer a recombinant Cupriavidus necator strain capable of utilizing lactose for polyhydroxyalkanoates (PHAs) production.
• To enhance PHA yields by reducing intracellular polymer degradation.
• To enable the use of waste materials like cheese whey as a carbon source for biopolymer synthesis.

Main Methods:

• Genetic modification of Cupriavidus necator DSM 545 by inserting Escherichia coli lac genes (lacZ, lacI, lacO) into the phaZ1 depolymerase gene via gene replacement.
• Construction of a recombinant strain (mRePT) with a disrupted phaZ1 gene and a synthetic promoter.
• Growth and PHA production studies using lactose, whey permeate, and hydrolyzed whey permeate as carbon sources.
• Inactivation of the phaZ3 depolymerase gene in the engineered strain.

Main Results:

• The genetically modified (GM) strain mRePT demonstrated the ability to grow and produce PHAs using lactose and whey-based substrates.
• The engineered strain exhibited lower intracellular PHA degradation compared to the wild-type strain.
• Higher PHA yields were achieved with the recombinant strain, demonstrating improved production efficiency.

Conclusions:

• The engineered Cupriavidus necator strain effectively utilizes lactose for PHA production, enabling the valorization of cheese whey waste.
• Disruption of the phaZ1 depolymerase gene and introduction of lactose metabolism genes enhance PHA yields.
• This work presents a promising strategy for sustainable biopolymer production from industrial byproducts.