Biodiesel made from discarded paper and cardboard

Researchers genetically modified a yeast to convert sugars to lipids more efficiently, a major step in biodiesel production.

In a study, a microorganism was developed that is capable of producing lipids from cellulose and xylose. Author: @emiliomoron, contains public domain images, wood, cardboard.

We know that the use of fossil fuels is the main source of greenhouse gases, with diesel being a fuel that contributes a large amount of fine particles and gases. So the use of biodiesel can be a measure that helps mitigate climate change caused by the emission of these gases. The problem with large-scale biodiesel production is the limited availability of raw material, since processing from virgin vegetable oil such as soybean or palm oil involves competing with food production for the raw material, or using waste cooking oils involves having large amounts of this oil, and it is a bit scarce.

But thanks to recent advances in the cellulosic bioethanol industry, the implementation of lignocellulosic biorefineries has been extended to the production of biodiesel, in which vegetable oils are replaced by microbial oils, thus increasing the sustainability of the process by reducing its environmental impact. Therefore, a great effort is being made to develop biofuels using lignocellulosic biomass generated as a by-product of activities such as agriculture or forestry, instead of consuming raw materials derived from food crops.

And of the many microorganisms that can be used for the production of microbial oils, the Yarrowia lipolytica yeast has emerged as one of the most promising strains due to its high capacity for lipid accumulation, its robustness in difficult environments and a fully sequenced genome, which makes this strain very attractive for the production of oils used for biodiesel.

A team from the Korean Institute of Science and Technology's (KIST) Clean Energy Research Center announced that they have developed a novel method using the Yarrowia lipolytica yeast to produce biodiesel precursor oils from lignocellulosic biomass, such as that obtained from discarded agricultural by-products, paper and waste cardboard boxes, as reported in the GCB-Bionergy magazine.

This microorganism was developed to produce biodiesel precursors during the process of metabolizing the sugars contained in the biomass it feeds on. This sugar contained in the lignocellulosic biomass is usually composed of 70% glucose and 30% xylose, and although the microorganisms are naturally efficient in metabolizing glucose, they do not feed very well on xylose, which limits the performance of the raw material. Therefore, a pathway for the utilization of xylose was constructed by introducing a gene of the mutated xylose isomerase (XylA), thus complementing the catabolic pathway of xylose in the Yarrowia lipolytica yeast, so that its native metabolism is completed with xylose, implementing a heterologous pathway with the use of xylose based on oxidoreductase, xylose reductase (XR) and xylitol dehydrogenase (XDH), which allowed it to produce lipids from xylose as a carbon source.

A schematic illustration of metabolic pathways for the bioconversion of glucose and xylose into lipids. Author: @emiliomoron.

In this study, it allowed the development of a microorganism capable of producing high performance lipids from xylose as a carbon source, which shows the potential of using waste biomass as an important source of raw material for the production of microbial oil for the purpose of producing biodiesel. What is clearly needed at a time like this, where we are living the consequences of climate change on a daily basis, is to obtain biofuels in a sustainable manner that will help reduce greenhouse gas emissions and can be used in existing vehicles.

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