Beneficial bacteria as natural biocontrol agents for preservation of fungal infested works of art – a review

Abstract

Fungal infestation is considered to be one of the main causes of decay of all types of historic works of art and source of occupational hazard for conservators, restorers and other personnel responsible for cultural heritage upkeep. Nowadays, adequate control method for suppression of fungal infestation, with minimal environmental impact, is still a considerable problem which requires a solution. Use of highly efficient inorganic and organic biocides to eradicate fungal growth, in heritage repositories and outdoor environment, is increasingly discouraged due to their toxicity, nonselective mode of action, abrasiveness, low long-term effectiveness and promotion of resistance. The need for environmentally friendly alternatives to toxic biocides has directed the research in last decade towards potential application of natural products, with new focus on beneficial bacteria due to possibility of implementing biotechnological approaches to obtain sufficient amounts of bioactive compounds. Although very limited in scope, up to date literature overview has clearly pointed out bacteria of Bacillus genus as promising green alternative for sustainable and long-term cultural heritage conservation due to their non-pathogenic nature, great physiological diversity, intensive sporulation, easy cultivation and manipulation, high metabolite yield, and ability to produce multitude of bioactive secondary metabolites, including antibacterial ribosomally nonribosomally synthesized peptides and lipopeptides. This makes production of Bacillus-biocompounds in industrial bioreactors ideal solution for large scale in situ application on infested works of art. Conducted research has demonstrated great potential of these biocompounds to suppress growth of biodeteriogenic fungi, isolated from multitude of works of art, in in vitro experiments, with activity sometimes being comparable or even higher than commercial biocides. Several studies performed on laboratory models in simulated conditions have confirmed antifungal activity as well as absence of any form of negative impact applied bacteria-based bioformulation might have on a structural or aesthetic integrity of treated models. Additional studies are, however, necessary to determine the most adequate method of application, evaluate the long-term effectiveness, potential recolonization, and determine the costs of its production and application, before usage of bacterial biocompounds becomes groundbreaking new norm in conservation practice that replaces commercial biocides.