The increase in sugar production, as well as the volume of sugarcane biomass (in this case, bagasse and husk), will make it possible to produce so-called second-generation ethanol, among other products.
Boost sugarcane productivity for the purpose of increasing bioethanol production. This is the main objective of the research study “Advances for sugarcane and new sources of bioenergy”, a project developed within the scope of the Research Centre for Innovation in Greenhouse Gases (RCGI), financed by Shell of Brazil and the São Paulo Research Foundation (FAPESP). “Cane produces sugar only once a year. We want to make this happen twice a year, like corn that has a main crop and the so-called ‘safrinha’ (a smaller follow-up crop),” says biologist and research Coordinator Marcos Buckeridge, who is the Director of the National Institute of Bioethanol Science and Technology (INCT), based in the Biosciences Institute of the University of São Paulo (IB-USP).
The INCT currently consists of 15 laboratories. Some of those laboratories participate in the RCGI project: the Laboratory of Ecological Physiology of Plants (LAFIECO), created by Buckeridge in 2005, and the Laboratory of Cellular Biology of Plants (BIOCEL), both located at IB-USP, in addition to the Laboratory of Plant Molecular Genetics, at the State University of Campinas (UNICAMP), and the Center for Nuclear Energy in Agriculture (CENA), on the Piracicaba campus of the Luiz de Queiroz College of Agriculture (ESALQ-USP).
“The first step of the study will be to sequence the sugarcane genome at the chromosomal level so that we can have a map of the plant’s genes,” says Buckeridge. “The genome is divided into chromosomes and the genes that coordinate biological functions are scattered among them. To understand how plant growth is coordinated, it is necessary to know the exact positions of each gene activated during growth.”
This is a major challenge, Buckeridge says. “Unlike human beings who have two copies of the genome in each cell, or even wheat with four copies in each cell, the sugarcane genome is extremely complex, because it has between eight and 12 copies per cell. This takes place because sugarcane is a hybrid resulting from a combination of two grass species originating in China. The hybrid, which we call sugarcane, has been genetically modified since the 16th century to adapt to the conditions of the planting site. It is practically a Frankenstein,” he jokes. “The problem is that this complicates the work of scientists, because it is difficult to discover which genome is responsible for a given function.”
The study will work with a system developed by one of the project team members, Diego Riaño-Pachón, Professor at CENA-USP. “He created models for three different methods that will be of immense value in achieving the sequencing of the sugarcane genome at the chromosomal level,” says Buckeridge. “The purpose of the first model is to combine classic sequencing strategies with a modern physical sequencing technique (PacBio) that allows obtaining sequences of large fragments of sugarcane DNA. This will make it possible to overlap those large pieces of DNA and understand where the chromosomes begin and end. The other two sequencing techniques can be overlapped, as well, and together, the three techniques should provide unprecedented precision regarding the sugarcane genome.”
With the genetic mapping of the plant in hand, the next step is to observe jointly the hormones and the plant’s sugar sensor system, in order to be able to understand how sugarcane grows, as well as its sucrose production process. “Thanks to research carried out by LAFIECO in 2018, we discovered that over the first three to six months, the sugarcane plant creates a huge capacity for storing sugar, mainly because of a set of genes that are called the sugar sensor system. It is during this period that the plant’s growth takes off,” says Buckeridge. “Now, we want to delve deeper into this process to understand how it happens. But we will only be able to do this if we also observe the hormones responsible for the communication system that informs the plant that it is time to grow. This step will be carried out with the collaboration of Professor Eny Floh, from BIOCEL-IB-USP.”
To make this analysis possible, the researchers will use the protein CRISPR-Cas9 (acronym for Clustered Regularly Spaced Palindromic Repeats, which work with an associated protein, CRISPR-associated protein 9). This is a genome editing tool developed by French microbiologist Emmanuelle Charpentier and American biochemist Jennifer Doudna who won the Nobel Prize in Chemistry in 2020 for this feat. “We are not going to develop a transgenic plant, because the editing process eliminates the need to insert foreign genes into sugarcane. In this case, editing the DNA, with a kind of cut-and-paste of genes, is enough for the purpose of altering selected genomic regions and, thus, re-engineer the functioning of the plant. Once the DNA is edited, we proceed to select the desired mutants that grow faster, accumulate more sugars and/or soften their own cell walls, in order to make the production of second-generation bioethanol easier,” Buckeridge explains.
The increase in sugar production, as well as the volume of sugarcane biomass (in this case, bagasse and husk), will make it possible to produce so-called second-generation ethanol, among other products. “This residue can be fermented and, thus, increase Brazil’s ethanol production by up to 40%. It is also possible to use polymers present in sugarcane fibers, such as beta-glucan, in anti-wrinkle cosmetics, or as a food supplement, and by the pharmaceutical industry as a potent natural antidiabetic,” Buckeridge says.
The experiments performed throughout the duration of the project will be tested via mathematical modeling. “Calculations based on reliable scientific data and physiological modeling, coupled with environmental data using artificial intelligence, should allow us to ascertain how our laboratory testing would work in the field, as well as how sugarcane might behave under extreme environmental conditions, such as water stress, temperature increase, and excess carbon dioxide,” Buckeridge explains.
New raw materials – Besides sugarcane, the project will work with two other raw materials. One of them is duckweed (Lemna minor, for example) – aquatic plant of the Araceae family, which is the same as lilies – and philodendra. “Duckweed is tiny and grows as fast as sugarcane. It can be used to produce bioethanol, because it produces biomass in massive quantities without needing to occupy soil. What’s more, these plants fight water pollution, can be used as a food supplement, and produce substances that potentially could be employed in the development of drugs against Covid-19,” Buckeridge adds.
The project team will also study soy residue. “It is produced in Brazil in greater quantities than sugarcane bagasse. Our plan is to discover new uses for this raw material. We are quickly learning how Brazilian soy responds to high atmospheric carbon dioxide combined with water stress and elevated temperatures,” the research leader says. “We already know that there are significant changes in chemical composition. For soybeans, we will have to follow a path similar to that of sugarcane and learn how its composition will be affected by global climate changes, in order to make the best use of this highly valuable biomass in Brazil,” Buckeridge concluded.