Seeking to overcome these drawbacks, IRD researchers (UMR 180) and INRA (UMR 1163) (1), working jointly within IFR-BAIM (Biotechnologies Agro-Industrielles de Marseille), have elaborated a new bioprocess that transforms the bagasse into paper pulp and also produces an industrially useful enzyme, laccase. The process is based on the metabolism of a filamentous fungus which, when raised in culture on bagasse in the presence of ethanol, produces this enzyme.
Laccase breaks down the lignin in the cane waste, changing the latter into paper pulp. Preliminary laboratory trials show that this integrated bioprocess can be adapted to other potential fibre-yielding materials, opening up promising applications for the paper industry.
The principal raw material used for manufacturing paper pulp is wood. However, growing demand in the paper industry, at a time of dwindling forest resources, have compelled the sector to turn to other sources of raw materials, such as cereal straw, reeds, bamboo or sugar-cane bagasse. This residue, obtained after crushing of the cane, is already used as a source of paper-making fibres in producer countries (in South America and India for example, where it represents 20 % of the paper production). The industry absorbs 10% of the world bagasse production. This material offers several advantages: rapid growth of the sugar-cane plant, widespread cultivation, lower energy and bleaching chemical requirements for bagasse refining. Such a process is also a convenient means of usefully clearing this voluminous sugar refinery waste product: indeed, one tonne of refined sugar results in two tonnes of bagasse.
However, whatever the raw material used, paper pulp has to undergo processing stages of delignification and bleaching to turn it into high-strength and durable paper. In some countries the chemical processing involved still entail the use of chlorine, dangerous for both health and the environment (2).
Research scientists from the IRD and INRA studied an alternative, biologically based, solution. Laboratory experimentation enabled them to develop a non-polluting process, which at the same time yields a delignifying enzyme, laccase, from a culture of a filamentous fungus and effectively recycles the sugar-cane bagasse. Its principle lies in the specific metabolic characteristics of this fungus, Pycnoporus cinnabarinus, which produces laccase naturally. This enzyme breaks down the lignin in the fibres of bagasse used as substrate in these trials, transforming this waste product, after mechanical refining, into paper pulp. As the lignin progressively disappears, the pulp obtained becomes bleached. This pulp can be used as it is to make cardboard, but it must undergo additional treatment using hydrogen peroxide in order to yield paper for printed and writing.
P. cinnabarinus naturally sythesizes only small amounts of laccase when it grows on bagasse. It is necessary to add volatile agents such as ethanol, in order to increase production of the enzyme under these conditions (3). Ethanol was chosen as a laccase-inducer in this study because of its abundance, its low toxicity and low production cost. The research team moreover showed that if it was put into the system by forced convection at a rate of 7 g of ethanol per m3 (concentration equivalent to 3° of alcohol in the liquid phase), laccase production increased, to a maximum level (90 U per g of dry bagasse support). This amounts to 45 times the yield obtained without ethanol. Moreover, it appeared that little or no ethanol introduced was consumed by the fungus which preferentially uses other sources of carbon, resulting from the bagasse (saccharose) or put in with the substrate (maltose, yeast extracts and so on). It can therefore be recycled in the system or eliminated in a second system associated with it (4).
Replication of the fermentation trials at a larger scale, in an 18 litre bioreactor, confirmed the efficiency of the laccase production obtained using bagasse and ethanol (90 000 U per kg of dry bagasse after 30 days, representing the quantity needed for processing, without input of fungus, an extra 4 kg of bagasse). This bioprocess resulted in a 50% saving in energy consumption required for paper pulp refining, compared with that recorded for refining pulp from bagasse that had not been biologically treated. Another benefit came in the form of a 35% improvement in the paper’s mechanical characteristics (tensile strength and tear resistance) without appreciable loss of material.
The results as a whole emphasize the potential for applications of this bioprocess in the paper industry. Retrieval of the laccase at the end of the cycle, after washing and pressing of the bagasse, allows additional quantities of the substrate to be processed and, in this way, raise the profitability of the operation. Furthermore, this process can be adapted to the processing of other raw materials (wood, cereals). Investigation of the use of methanol as laccase inducer can, similarly, be envisaged as a way of recycling this compound, which constitutes one of the main pollutants emitted by the paper industry.
(1) Each of these teams is a partner of the Universities of Provence and the Mediterranean . They are grouped together within the research entity IFR 86-BAIM.
(2) In Europe, however, the paper industry is turning increasingly towards completely chlorine-free processes.
(3) Lomascolo et al.- Overproduction of laccase by a monokarryotic strain of Pycnoporus cinnabarinus, using ethanol as inducer, J. Appl. Microbiol. 2003, 94, p. 1-7.
Other research conducted by the IRD, working jointly with the UAM (Autonomous University of Mexico) of Mexico City and the ICIDEA (Cuban Institute of Research on Sugar-cane derivatives) of Cuba, have shown that a yeast, Candida utilis, can be used to produce biomass on the bagasse. It can thus provide a protein-rich feed for animals, while eliminating ethanol in the process (air pollution removal). See the scientific bulletin n°155, May 2002, on line on www.ird.fr/fr/actualites/fiches/2002/fiche155.htm.
Marie Guillaume | alfa
Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University
New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering