The scientists who re-engineered the plastic-eating enzyme(酶) PETase have now created a new enzyme called “cocktail” , which can digest plastic up to six times faster.

PETase breaks down PET back into its building blocks, creating an opportunity to recycle plastic and reduce plastic pollution. PET is the most common thermoplastic(热塑性塑料) used to make single-use drinks bottles, which takes hundreds of years to break down in the environment, but PETase can shorten this time to days. The initial discovery set up the prospect of a revolution in plastic recycling, creating a potential low-energy solution to tackle plastic waste.

Now, the same trans-Atlantic team have combined PETase and its “partner”, a second enzyme called MHETase, to generate much bigger improvements: simply mixing PETase with MHETase doubled the speed of PET breakdown, and engineering a connection between the two enzymes to create a “super-enzyme”, increased this activity by a further three times.

The team was co-led by the scientists who engineered PETase, Professor John McGeehan and Dr Gregg Beckham. Professor McGeehan said: “Gregg and I were chatting about how PETase attacks the surface of the plastics and MHETase chops things up further, so it seemed natural to see if we could use them together. Our first experiments showed that they did work better together, so we decided to physically link them. It took a great deal of work, but it was worth the effort — we were delighted to see that our new enzyme is up to three times faster than the separate enzymes.”

The original PETase enzyme discovery indicated the first hope that a solution to the global plastic pollution problem might be within grasp, though PETase alone is not yet fast enough to handle the tons of PET bottles. Combining it with a second enzyme, and finding together they work even faster, means another leap forward has been taken towards finding a solution to plastic waste. PETase and the new combined MHETase-PETase both work by digesting PET plastic. This allows for plastics to be made and reused endlessly, reducing our reliance on fossil(化石) resources.

Tiny sensory hair cells called stereocilia(静纤毛)located in your inner ear are responsible for detecting sound. When these become damaged, either by genetic disorders, loud sounds or old age, it can lead to hearing difficulties and even deafness.

Now, in a series of experiments on mice, researchers based at the Salk Institute for Biological Studies and the University of Sheffield have identified a protein that can be delivered to these hair cells in order to stimulate their growth. “Our discovery shows that hair cell function can be restored in certain cells,” said Dr Uri Manor, assistant research professor and director of the Waitt Advanced Biophotonics Core at Salk.

Stereocilia hair cells are found throughout the cochlea(耳蜗). Regions of the cochlea that sense low frequencies have longer stereocilia, while regions that sense high frequencies have shorter stereocilia. When sounds enter the ear, they cause fluid within the cochlea to vibrate(振动), which in turn causes the stereocilia to move. These hair cells then send signals to neurons(神经元), which pass on information about the sounds that we are hearing to the brain.

In their previous studies, Manor and Prof Walter Marotti found that the protein EPS8 was involved in determining the length of stereocilia. Without the protein, the growth of the hairs is stunted and they remain very short. For this latest study, the two researchers teamed up to design an experiment to see if adding EPS8 to stereocilia hair cells could stimulate their regrowth and improve hearing in mic. They used a common gene therapy(基因治疗)technique to deliver the protein to the hair cells on the back of a virus. They then investigated the effects using imaging techniques.

The team found that EPS8 increased the length of the stereocilia and restored their function in low-frequency cells, although not enough to restore the hearing of the mice. However, they also found that the cells seemed to lose their ability to regenerate as they aged. The researchers now plan to investigate the action of EPS8 further, with the hope of extending the age range over which it is effective.