Ecological Engineering and Environment Protection, No 1, 2019, p. 71-78 doi.org/10.32006/eeep.2019.1.7178 This article is distributed under the terms of the Creative Commons Attribution License 71 LABORATORY BIODEGRADATION OF POTENTIAL CELLULOSE WASTES GENERATED DURING LONG-TERM MANNED SPACE MISSIONS Najdenski H. 1 , V. Ilyin 2 , P. Angelov 3 , V. Hubenov 1 , D. Korshunov 2 , V. Kussovski 1 , L. Dimitrova 1 , I. Simeonov 1 1 The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences 2 Russian Federation State Scientific Center - Institute for Biomedical Problems, Russian Academy of Sciences 3 Space Research and Technology Institute, Bulgarian Academy of Sciences Abstract: Anaerobic microbial biodegradation of cellulose containing wastes generated during the long-term manned space missions is a key technological approach for resolving the problem of wastes accumulated onboard of the spacecraft. Herewith are presented data on the possibilities of structurally stable multispecies microbial consortia originating from methanogenic bioreactors to decompose different cellulose substrates – filter paper, medical gauze and vegetable mix as potential cellulose wastes during space missions. The rates of biodegradation processes carried out at mesophilic and thermophilic conditions are not only measured and compared but are providing new opportunities for development of technology for microbial biodegradation of cellulose-rich organic wastes. Moreover, the studies have shown that paper and gauze hydrolysis with the help of cellulolytic bacterial communities can be an effective component of utilization of cosmonaut hygiene items. Biodegradation of plant wastes by community of anaerobic bacteria is promising and applicable tool also under terrestrial conditions. Light microscopy of bacterial communities reveals the presence of Gram-positive spore forming bacilli (short and long forms, bipolar and dividing cells) and typical clostridia forms. Keywords: cellulose containing wastes, biodegradation, anaerobic digestion, bacterial consortia, long-term manned space missions INTRODUCTION Planned in the near future, space flight to Mars and others long-term manned space missions raise a number of impressive issues for modern science. One of the most important item is how to dispose of crew organic waste during space mission. The relative proximity of the Earth allows the waste from the International Space Station (ISS) to be removed through the container and burst into the atmosphere. During the expedition to Mars or Moon for example, it will be impossible since this garbage cannot be thrown into space and this requires its recycling. Investigations on this problem are conducted intensively in the leading space countries in the world. An international group of experts is working on the creation of a closed ecosystem in the framework of MELiSSA project at the European Space Agency [Lasseur et al., 2006; Hendrickx et al., 2010]. In the frame of the project, organic waste are disposed of different groups of bacteria in special bioreactors. The goal is to get water from the disposal of this waste, which will be used for the space greenhouse, or some kind of gas that would serve as a source of energy. Scientists will investigate the behavior of terrestrial bacteria in microgravity on the ISS. Investigations on the ability of microorganisms for waste utilization in space conditions date back to the first piloted spaceflights. The variety of microorganisms used for research at such conditions is considerable. This includes: viruses, bacteria, fungi [Benot and Klaus, 2005; Taylor et al., 1975]. For example, the main microorganisms tested on board of the spacecraft "Apollo 16" and the satellite "Biokosmos 2044" were representatives of the species: Bacillus subtilis, Aeromonas proteolytica, Bacillus thuringiensis, Escherichia coli, and the fungus Trichosporon terrestre, Saccharomyces cerevisiae, Rhodotorula rubra [Bouloc and D’Ari, 1991; Taylor et al., 1975]. American researchers [Chynoweth et al., 2006.] have conducted anaerobic digestion of organic wastes (domestic, agricultural, paper, etc.) under the ground gravitation conditions. They have created a variant of their earlier patented apparatus [Chynoweth and Legrand, 1993] to operate on board the spacecraft, i.e. in microgravity. Different cellulosic wastes like hygienic materials, food refuse, paper, cotton, clothing, wipes, grey tapes etc. show different potential for biodegradability due to their specific lignocelluloses structure [Pullammanappallil and Dhoble, 2010]. The general structure of lignocelluloses from plant cell walls for example, contains a mixture of polysaccharides of high molecular weight. The major components are cellulose, hemicellulose, and lignin. Cellulose is a structural polymer of glucose residues joined by β-1,4 linkages.