It’s no secret that plastic bags have been causing problems around the world. In Bangladesh, they were clogging drain pipes and causing sewage to overflow.
These disposable bags linger for decades after they are discarded, along with other non-biodegradable waste.
But are they really non-biodegradable?
What if these bags could be disintegrated? And what if a process to do this was already occurring in places we haven’t considered?
That possibility has driven the research of Dr. Tabassum Mumtaz. Since pursuing her graduate studies, and now as Principal Scientific Officer for the Bangladesh Atomic Energy Commission (BAEC), she has been investigating ways to harness natural processes to address environmental problems. Specifically, she focuses on the bioconversion of waste byproducts and biomass into more environmentally-friendly compounds.
This year, she was honored with the OWSD-Elsevier Foundation Award for Women Scientists in the Developing World.
Tabassum’s research career began in 2000 when she started her master’s thesis at the University of Dhaka, Bangladesh, under the direction of Prof. Dr. Mahbubar Rahman Khan, head of the microbiology laboratory in the botany department. “My topic was driven by the banning of polyethylene shopping bags in Dhaka City by the government of Bangladesh, which had a great impact on environment and society,” she said. “We have the mentality of using and throwing here and there, and the lack of segregation of waste was resulting in environmental pollution, especially in the city.”
What exactly happens to the material of those bags after they’re discarded? Tabassum and her supervisor set out to find out.
“When we throw away a plastic bag with food waste or any other waste, bacteria come in contact with that plastic,” she said. “So we were thinking, ‘Is that bacteria staying on it or just using it as a support – or are they trying to utilize it in some way?’”
Under the microscope, they saw colonies of bacterial cells growing on the surface of the plastic.
[The bacteria] were using something from the plastic as their carbon source to grow. So what is it? Polyethylene has only hydrogen and carbon, nothing else, but the bond is very strong, so it’s very difficult for bacteria to degrade it without having an enzyme.
Then they witnessed something else that gave them pause:
We saw a microscopic perforation, like a hole – a very, very tiny hole.
Still, it was just microscopic evidence. To prove that the bacteria were growing on the plastic and consuming it, they would need to examine the process step by step.
One year was too short to study the association of bacteria on waste plastic film. During her master’s study, they isolated some bacteria from these samples and characterized these strains as species of Bacillus and Planococcus.
After finishing her master’s degree, she continued her investigation as part of the university’s MPhil program while also working as a post-graduate research fellow in the Fibre and Polymer Division at the Bangladesh Council of Scientific and Industrial Research (BCSIR). With Prof. Khan as her mentor, she studied how the bacterial process occurred when the bags were steeped in natural soil. Over two years, they buried thin sheets of polyethelene, unearthing them each month to document the process of colonization.
Two years was not enough time to complete this research, however, so after finishing her master’s degree in science, she continued her investigation as part of the university’s MPhil program while also working as a post-graduate research fellow in the Fibre and Polymer Division at Bangladesh Council of Scientific and Industrial Research (BCSIR). With Prof. Khan as her mentor, she studied how the bacterial process occurred when the bags were steeped in natural soil. Over two years, they buried thin sheets of polyethelene, unearthing them each month to document the process of colonization.
‘Are you sure you can do it?!’
Though it was a clever idea, some of their colleagues were skeptical.
It was an ambitious project, and people said, ‘Are you sure you can do it?
With limited resources – a common problem in the developing world – the odds were against them. For example, after identifying the bacteria, they wanted to radiolabel the carbon in the plastic to see whether that carbon has been used by the bacteria. “It’s a very sophisticated technique,” Tabassum explained, “but we couldn’t do it with our limited resources.”
Fortunately, they did have facilities to do phase contrast microscopy and florescent microscopy in their laboratory, which would enable them to see the cells in a different color from the material so they would be easy to differentiate.
Over time, they saw holes in the polyethelene film: “Bacteria grows on it, then they disintegrate the material into very small pieces,” she noted. “At the end of our study, we could see some mixed with the soil so we couldn’t retrieve it all.”
Interestingly, that happened with the transparent sheets, not the black ones that had a color additive. But again, without evidence from a scanning electron microscope, they could not confirm their observations in lower magnification micropscopic views.
Still, they persisted, using ingenuity and resourcefulness to find a solution. Each month, Prof. Khan carried the weathered samples to Jadavpur University in India, paying for his airfare and travels out of pocket. “He was very passionate about this research, and I owe him – in fact – everything,” Tabassum said. “He used to say, ‘Research gives you the purpose of life,’ which I always recall. From him, I got this inspiration of doing research.”
Their photographs from the scanning electron microscope were very convincing in validating their prediction of environmental degradation.
Therefore, they concluded that this process was not taking place in isolation.
In the environment, a lot of factors are coming into play: you have light, you have heat, you have wind. So with deterioration and decomposition, which deal with biological means, some changes take place, even though it’s on a very, very small scale.
Though small-scale, the process they observed gave them an idea for an application: if a cocktail of bacteria is shown to disintegrate plastic, it could be cultivated in larger quantities and added to the environment where needed.
Her vision extends far: “In the ocean, we have so much plastic waste, so we can use that cocktail of bacteria to clean up the environment.”
She published the results in Elsevier’s Micron journal with co-authors Prof Khan and her supervisor at UPM, Prof. Dr. Mohd Ali Hassan: “Study of environmental biodegradation of LDPE films in soil using optical and scanning electron microscopy.”
Converting industrial waste to environmentally friendly products
In 2005, Tabassum moved to Malaysia to pursue her PhD in Environemntal Biotechnology at Universiti Putra Malaysia (UPM) with a fellowship from OWSD (the Organization for Women in Science for the Developing World).
Her doctoral research was part of an adacemic-industry collaboration between MIT, Malaysian universities and the palm oil industry. Their research project – “Bioconversion of Palm Oil and its Products to Polyhydroxyalkanoates (PHA) Biodegradable Plastic” – focused on converting waste streams from palm oil product into usable products. The project Tabassum chose involved producing biodegradable plastics (PHBV) from palm oil mill effluent (POME) using mixed organic acids. Later on, she also researched the production of biohydrogen from POME and food waste as substrate.
“When I went to Malaysia, my supervisor said I can choose any project he had,” she recalled. “One project was with polyhydroxyalkanoates, or PHAs, which is actually a biodegradable plastic of microbial origin. It’s a solution that I addressed during my previous study, so I was very enthusiastic about doing it.”
She used mixed organic acids as food to produce plastics from bacteria, which was challenging for two reasons. First, it required extracting a mixture of organic acids produced from palm oil wastewater after anaerobic digestion in large quantities, and second, she had to feed this mixture to plastic-producing bacteria without changing its composition.
Bacteria degrades the wastewater into organic acid, so [we tried to] extract those acids only from the wastewater. But you cannot separate those acids or change the ratio – it’s a cocktail of acids, and you have to use it just like you got it.
In nature, anaerobic digestion of wastewater results in the formation of organic acids, she explained. So partially digested palm oil wastewater containing organic acids were separated from the wastewater and digested with concentrated acid and finally evaporated as a clear solution of mixed organic acids.
They successfully develop an extraction protocol to be applied in pilot scale for the extraction of organic acids from palm oil wastewater, for which they won a gold medal in UPM’s Inter-University Invention, Research and Innovation Exhibition in 2010.
The other bottleneck in this project was very low cell titer.
“It was very difficult to cultivate the bacteria in large amounts,” Tabassum said. “They don’t grow well. It’s likely because organic acids like acetic acid (the one we use for vinegar), propionic and butyric acids are not good food for bacteria. You cannot use them in high concentrations. So you have to add a little bit at a time so it doesn’t go to that level which again inhibits the growth of the bacteria. It was a very difficult thing to do.”
As often happens, challenge sparks innovation. Tabassum developed a strategy to feed these acids to keep the pH balanced. “pH is very crucial for the bacteria,” she explained. “Adding the acids in small increments will adjust the pH and at the same time provide food for the bacteria in a way that won’t harm the cells. In high concentration, the bacteria will die.
“From that feeding strategy, surprisingly I got 80 percent over accumulation. And we could analyze the property of the polymer.”
She could not have executed this research plan in her home country of Bangladesh because of limited laboratory resources. She said her lab is not equipped with high-throughput analytical tools like HPLC (high performance liquid chromatography) and GC(gas chromatography) as well as essentials for polymer analysis. Also, it’s not possible to stay in the laboratory overnight to work continuously because of security issues.
At BAEC, Tabassum is focusing on the isolation of bioplastic PHAs, which are important for the environment because they can be produced by bacteria from renwable resources and they are completely biodegradable in nature. Her projects involve the isolation of bioplastic PHAs producing bacteria from compost, wastewater and food waste. She is among just a few researchers in Bangladesh with expertise in PHA-related research.
She is cultivating bacteria from irradiated wastewater because they are resistant to gamma radiation and therefore suitable for use in radiation contaminated area. She is looking into the application of gamma radiation on wastewater decontamination while also checking the ability of radio-resistant bacteria to synthesise bioplastic PHAs – an area that has not been studied widely. While PHA-related research has expanded significantly in terms of bacterial diversity, gentic manipulation and carbon sources, Tabassum said, so far, no literature has reported on PHAs derived from radio-resistant bacteria.
In the coming years, she is hoping to work on biomass utilization to produce biohydrogen and bioethanol. She believes that strategies that focus on pollution abatement and the concurrent generation of renewable energy (biogas, biohydrogen) and valuable green bioproducts (organic acids, bioplastics) can only be achieved through academia-industry collaboration. For example, she said, the collaboration between dyeing industry and her research lab in BAEC can solve some practical issues in industry while improving the scenario of wastewater treatment in Bangladesh.
These developments will eventually have a big impact on the energy sector of the country, she added. As for her own career, she is keen pursue research “with a freedom to design, develop and deliver research programs in the field of environmental science.” She sees herself working with a multinational research group active in the fields of solid waste management, environmental science, green economy and sustainable development.
Advice for young researchers
Tabassum has never taken the easy route with her research, focusing instead on what she has wanted to accomplish in the world of science. That experience inspires the advice she gives to students pursuing science as a career:
You have to be truthful to yourself, believe in yourself. No matter how hard it is, you will succeed if you keen trying again and again. And if you don’t accomplish what you are targeted to, discuss that with your supervisor.
Sometimes it happens that things don’t work in the way they think of. So you need to change the objective; you need to accommodate your objective – which I learned from my experience. It took a long time – five years – for me to get my PhD, but the good part is that I got six publications [as first author].
To date, Tabassum has 30 publications in highly ranked journals. She has won various awards and grants, but she considers the OWSD-Elsevier Foundation Award to be a highlight. After learning of her selection, she wrote:
Winning this award is like receiving an Oscar to me. This will be a tremendous inspiration to me and to all women scientists in Bangladesh and in the Asia-Pacific region — to dream and do research beneficial to the environment and society.