Lead by professor Fuzhong Zhang, the team was aiming to create a protein that forms ‘β-nanocrystals’, a significant component of natural spider silk.
“Spiders have figured out how to spin fibres with a desirable amount of nanocrystals,” said Zhang. “But when humans use artificial spinning processes, the amount of nanocrystals in a synthetic silk fibre is often lower than its natural counterpart.”
The university team designed a protein molecule that includes amyloid sequences – which have a tendency to form β-nanocrystals – and less repetitive amino acid sequences than spider silk to make them easier for engineered bacteria to make.
The bacteria produced a polymeric amyloid protein with 128 repeating units – the material that yielded the strength and toughness figures above after spinning. It “is stronger than common steel” and its “toughness is higher than Kevlar”, said the university. “Its strength and toughness are even higher than some reported natural spider silk fibres.”
The work is covered by in the journal ACS Nano as ‘Microbially synthesized polymeric amyloid fiber promotes β-nanocrystal formation and displays gigapascal tensile strength’.
Chart and image courtesy of researcher Jingyao Li