In a spacious refuse transfer station, the refuse sorted by categories was heaped into small knolls. Here, only the largest quantity of discarded plastic is found, such as discarded plastic foam, plastic toys, plastic teacups, plastic benches, and plastic bags utilized for packaging food. According to statistics, 20 tons of plastic are consumed every second globally, and 13 million tons of plastic flow into the ocean annually. These enduring plastic waste materials have evolved into a worldwide predicament and a vexation for sanitation workers.
If at this precise moment, a diminutive carabid larvae twists its feeble body, stands atop a hill, proudly thumps its chest, and asserts confidently: “I have amassed all these abandoned plastics. In a short span, I shall be capable of entirely decomposing them!” Upon hearing this, do you scoff like me, disapprovingly, and chuckle at this diminutive creature that speaks with such conceit?
So, what distinctive faculties do carabid larvae possess?
The principal constituent of the plastics we employ in our lives is colorless and translucent polystyrene, which possesses a glass transition temperature surpassing 100°C. Owing to the peculiar structure of its molecules, ordinary microorganisms find it arduous to degrade. Furthermore, polystyrene constitutes a substantial proportion of plastic waste, and its recalcitrance in degradation has imposed an enormous burden on the global environment. However, researchers have recently undertaken certain experimental investigations and substantiated that plastic can be decomposed by a carabid larvae that is more prevalent in warm and arid regions.
A collaborative research team comprising several preeminent chemistry professors worldwide has, for the first time, discovered that carabid larvae can consume polystyrene and diminish its mass and molecular weight through digestion. Even more astonishing is the scientific confirmation that intestinal flora derived from carabid beetle larvae can oxidize and alter the surface properties of polystyrene films.
Why are these carabid beetle larvae capable of degrading polystyrene within plastics?
The scientific research team isolated and identified Serratia within the intestines of carabid larvae. Following two weeks of feeding the larvae with polystyrene, they observed a sixfold increase in the proportion of Serratia within the larvae’s intestinal flora, accounting for 33% of the total intestinal flora. Additionally, the team discovered that the gut microbiota of carabid beetle larvae consists of a simple consortium of bacteria, which markedly differs from the gut microbiota of other insects previously found to possess the ability to degrade polystyrene.
What the scientific research team could not fathom was that 100 carabid beetle larvae could consume 34 to 39 mg of foam plastic daily, particularly plastics that are thin, pliable, and highly expanded. Half of the plastic ingested by these carabid larvae is converted into carbon dioxide, while the remaining half is transformed into biodegradable particles akin to rabbit excrement and excreted from their bodies, causing no pollution to the natural environment.
The study demonstrates that predatory beetle larvae exhibit specialized feeding habits, thereby suggesting that polystyrene can be decomposed by other insects that subsist on decomposing wood.
By employing bacterial strains capable of plastic degradation, isolated from carabid larvae, and replicating the uncomplicated intestinal flora of carabid larvae, researchers may potentially degrade polystyrene in a wholly biodegradable manner, thereby offering a resolution to the global predicament of plastic pollution.