Some very exciting breakthroughs have been made recently in using fungii and sugars to break through tough wood cellulose cell walls and access the abundant energy inside to make various types of fuel. Producing fuels from plants and other renewable sources requires breaking down the chemical cellulose, which traditionally has required the same amount of energy as is released when the cellulose cell walls are broken.
Scientists recently found a major candidate to drive, or catalyze, this stubborn chemical is a ubiquitous microorganism called Clostridium thermocellum that works well in hot environments without oxygen. Researchers found that C. thermocellum uses a previously unknown mechanism to degrade cellulose, in addition to other known degradation mechanisms.
Cellulostic Biomass Fuel Research: New Developments 2016
This discovery helps explain C. thermocellum’s superior ability to digest biomass and demonstrates the highly diverse strategies evolved in nature for bio-mass conversion, according to a new study published in Science Daily June 30. Researchers are using the study’s findings to develop optimal systems for breaking down plant matter to produce biofuels and biobased chemicals.
Lignocellulosic biomass is the largest source of organic matter on Earth, making it a promising renewable feedstock for producing biofuels and chemicals. Currently, however, the main bottleneck in biofuel production is the low efficiency of cellulose conversion, which leads to high production costs. To date, C. thermocellum is the most efficient microorganism known for solubilizing lignocellulosic biomass. Its high cellulose digestion capability has been attributed to the organism’s efficient cellulases consisting of both a free enzyme system and a tethered cellulosomal system, where multiple carbohydrate active enzymes are organized by primary and secondary scaffolding proteins to generate large protein complexes attached to the bacterial cell wall.
Recently, US Department of Energy BioEnergy Science Center (BESC) researchers discovered that C. thermocellum also expresses a type of cellulosomal system that is not bound to the cell wall, a “cell-free” cellulosomal system.
A link to the report can be found here: https://www.sciencedaily.com/releases/2016/06/160630102510.htm
Elsewhere, US-based scientists have altered the lignin in aspen trees in a way that increases access to biofuel building blocks without inhibiting plant growth.
The scientists based at the Department of Energy’s Brookhaven National Laboratory and collaborators have been able to do this by engineering a novel enzyme involved in lignin synthesis.
Lignin is a natural component of plant cell walls, the scaffolding that surrounds each cell and plays a pivotal role in plants’ ability to grow against gravity.
However, lignin is a problem for scientists interested in converting plant biomass to biofuels and other sustainable bio-based products. Lignin makes it hard to break down the plant matter so its carbon-rich building blocks can be converted into forms suitable for generating energy or running automobiles.
The scientists at Brookhaven said previous attempts to manipulate plants to produce less lignin have resulted in weaker plants and stunted growth, which has “put brakes on biomass production”.
However, their research, described in Nature Communications June 29, resulted in an almost 50 per cent increase in ethanol yield from healthy aspen trees whose woody biomass released 62 per cent more simple sugars than native plants.
Lignin makes up about 20 per cent of aspen’s woody structures, with cellulose and hemicellulose polymers making up approximately 45 and 25 per cent, along with other minor components.