Category: News

A new machine learning tool can analyse wines’ chemical profiles and use this to accurately predict where they were produced. The system could aid the wine industry’s efforts to authenticate the origins of its products.

Each wine has a complex chemical profile, which is shaped by things like the soil and climate of the area where the grapes were grown – its terroir – as well as the individual practices of the wine producer. While individual molecules can have a big impact on a wine’s flavour and can provide key insights as to where the wine was produced, the vast array of compounds within any wine makes analysing it a difficult task.

A research team led by Stéphanie Marchand from the University of Bordeaux, France, and Alexandre Pouget from the University of Geneva, Switzerland, developed a machine learning system to analyse the full chemical profiles of various wines. The machine learning algorithms analysed unprocessed gas chromatograms of 80 different wines produced across 12 harvest years at seven wine estates in France’s Bordeaux region. From this information, the system could deduce which wines were produced on the same estates with 100% accuracy. The system deduced the wines’ vintage with 50% accuracy.

The researchers note that it remains to be seen how their GC-based classifier would perform when provided with the chemical profiles of wines from beyond the Bordeaux region. They also state that it would be interesting to compare the performance of their system with an expert human wine taster in a blind taste test.

Nylon-6 can be rapidly broken down by a new catalytic process without generating harmful byproducts or requiring toxic solvents. The metallocene catalytic system, which is based on earth-abundant early transition and lanthanide metals, depolymerises the material at unprecedented rates.

Using this catalyst, the team was able to recover 99% of the nylon-6’s monomers, which could then be upcycled into higher-value products. The system is also highly selective and only acts on nylon-6. Consequently, the researchers suggest that it could be applied to large volumes of unsorted waste.

This new system is also greener than other catalysts that have previously been investigated, which rely on high temperatures, high-pressure steam or toxic solvents.

In contrast, the catalytic process developed at Northwestern University in the US doesn’t depend on expensive materials or extreme conditions. The catalytic system involves lanthanide metal ions encased in a specially designed organic ligand framework. To recycle these resilient plastics, these catalysts must be tailored to not only be highly active, but also thermally stable and robust to handle and break down these polymeric materials.

The researchers also relied on high-level quantum mechanical calculations to examine the energetics of various possible catalytic reaction pathways and help guide them in designing the catalyst.

‘You can think of our catalyst as almost a Pac-Man – it starts at one end of the polymer and chomps along it and spits out the original monomer, called caprolactam,’ explains Tobin Marks, the study’s senior author. ‘And caprolactam actually comes out as a vapour so there’s no solvent, and we collect it – we cool the vapour and it forms very pure caprolactam.’

The catalyst moves down the polymer chain, rapidly expelling the caprolactam monomer molecules one by one. Its molecules can also jump from one chain to another. ‘We show in the paper that the catalyst can be recycled multiple times without slowing down, arguing that it can be used in a continuous process in which nylon is continuously fed to the reactor and caprolactam continuously exits from the reactor as would be done in a large plant,’ Marks states.

‘We understand through these computational works that our metal catalysts bind with the amide bonds of these nylon-6 polymers and start to “unzip” these plastics with monomers releasing at the polymer chain end,’ explains Liwei Ye, the paper’s first author. ‘These computational studies are important because they guide us, as experimental chemists, how to better design our catalytic structures and to make these processes more efficient.’

The Northwestern team has demonstrated that their new catalytic process can target nylon in a mixed plastic waste stream. ‘And now we’re looking at other mixtures, so that’s the next step of our research,’ he says. ‘Interestingly, there is an increasing demand especially for high end clothing made from recycled nylon, because people want to see that environmental sustainability consciousness.’

Beyond catalysis?

Marks and colleagues report a new π-ligated class of metallocene catalysts. They hope that it can now be used on a large scale to help tackle the global plastic waste problem.

Collin Ward, a marine chemist at Woods Hole Oceanographic Institute in Massachusetts, US, who was not involved in the work but researches how plastic degrades in the environment, says the study offers ‘a creative and novel way’ to recycle nylon. ‘I’m impressed with the number of experimental variables they considered when evaluating the effectiveness of the catalysts, showing great promise of the catalyst across many important test conditions.’

The logical next step, according to Ward, is to understand how feasible it is to scale this technology. ‘If successful, I agree with the authors that the technology could increase the circularity of nylon consumer products and reduce the amount of nylon that ends up in landfills,’ he says.

Yutan Getzler, an expert in polymer chemistry and recycling at Kenyon College in Ohio, says the problem with nylon-6 recycling is not one of chemistry, but economics. There are very well-established industrial processes to recycle nylon and resell it as other products, ‘but the question of whether or not they’re operating effectively really has to do with fluctuation in the price of petroleum, which is what’s going to define the price of petroleum-derived caprolactam relative to a chemically recycled material’, he explains. ‘You just can’t get enough of it to run a process efficiently at industrial scale, and that is not a problem that’s solved by catalysis.’

Liwei Ye’s name was corrected on 6 December 2023

Researchers in India have shown that an amphiphilic molecule can enhance the bactericidal activity of obsolete antibiotics by helping such drugs accumulate within Gram-negative bacterial cells.

Antimicrobial resistance mechanisms in bacteria include reducing the permeability of their outer membrane and efflux pumps that extrude antibiotic drugs. The growing creep of drug-resistant infections means we are in urgent need of new antibiotics that bacteria have never encountered and lack a mechanism to resist. But drug development is slow and costly, compelling the scientific community to explore other ideas.

Administering an adjuvant molecule alongside an existing antibiotic is one such alternative. Some adjuvant molecules aid antibiotic delivery by permeabilising cell membranes and suppressing efflux pumps. But a notable drawback typically associated with these adjuvants is their lipophilicity. This characteristic enables antibiotics to pass through both bacterial and mammalian cell membranes, resulting in non-selective cell death.

Now, Jayanta Haldar and colleagues at Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) have designed and finely tuned the chemical make-up of a new molecular adjuvant to make it biocompatible with mammalian cells. Their adjuvant molecule features long hydrophobic chains to improve membrane permeability, accompanied by ethanol groups for amphiphilicity and to induce specific hydrogen bonding interactions with Gram-negative bacterial membranes.

Halder’s team initially tested their molecular adjuvant in combination with the antibiotics rifampicin, fusidic acid, minocycline and chloramphenicol before deciding to focus on fusidic acid. In a cellular assay, a combination of fusidic acid and the molecular adjuvant was effective against biofilms produced by Acinetobacter baumannii, a type of bacteria that is responsible for many drug-resistant infections. Not only did the adjuvant enhance membrane penetration, it also inhibited efflux pumps, allowing fusidic acid to accumulate within the bacterial cells. The combination did not appear to be toxic to mammalian cells and had potent antibacterial activity in a mouse skin infection model.

However, Halder’s lab did observe high lethality when administering the adjuvant intravenously to mice. The impact of this adjuvant on mammalian toxicity is therefore ‘still something to be discussed and debated’ says Nathaniel Martin, a professor of biological chemistry at Leiden University in the Netherlands. Another consideration for systemic application, says Martin, is the need for both molecules to locate the bacteria at the same time and place, requiring a match in their pKa profiles. Martin says that ‘this is an aspect that will need to be addressed and optimised’ in the future.

The research team at JNCASR acknowledges that devising a suitable delivery system for the adjuvant and antibiotic will be challenging. JNCASR team member Riya Mukherjee says they next need to perform in-depth mechanistic studies and pre-clinical efficacy tests. Mukherjee also mentioned the need for monitoring resistance development, as ‘although the combination therapy may be initially effective, there is always a risk of bacteria developing resistance over time’.

Despite the pitfalls, Martin says that ‘the use of adjuvants to tailor the properties of existing antibiotics … can definitely be part of the solution’ in the fight against Gram-negative superbugs.