MICROBIAL BIOCONVERSION OF CELLULOSE-CONTAINING WASTE IN TERRESTRIAL AND SPACE CONDITIONS

Abstract

One of the important ecological problems at present is the increasing pollution of the natural environment with cellulose waste. A similar process is also observed in long-term manned space flights: a huge amount of cellulose waste from clothing, hygiene materials, food residues and others accumulates, the processing and utilization of which is a definite scientific challenge. In recent years, many scientists have expanded and deepened their research on this important question, which still remains unresolved both in Earth’s conditions and during the long-term space flights. Many experiments are carried out on the biodegradation processes of cellulose-containing waste with the use of different populations of microorganisms – bacteria, fungi, etc., as well as with different parameters of the culture medium – composition, temperature, presence of oxygen, pH, etc. The synergistic action of these microbial populations, which have the capacity to degrade and assimilate complex carbohydrates (cellulose, hemicellulose and lignin) through the synthesis of a number of cellulolytic enzymes, thus restoring the carbon cycle in nature, has been proven. In parallel, research is being conducted in simulated microgravity conditions, focused on their future application for bioconversion and efficient utilization of waste in closed life support systems during long-duration manned space flights. An important condition is that the microorganisms used are not pathogenic, not resistant to antibiotics and do not form biofilms. There is already accumulated experimental data proving that microgravity conditions lead to changes in bacterial gene expression, growth rate, reduced motility, increased virulence, biofilm formation, etc. In this review, the most important results achieved by Bulgarian and foreign teams in this current and promising scientific field are briefly presented.