Isolation and selection of cellulose-chitosan degrading bacteria to speed up the mineralization of bio-based mulch films

Rossana Sidari^1*Marco Pittarello¹Maria Teresa Rodinò¹Maria Rosaria Panuccio¹Gabriella Lo Verde²Vito Armando Laudicina²Antonio Gelsomino¹

• ¹Mediterranea University of Reggio Calabria, Reggio Calabria, Italy
• ²Department of Agricultural, Food and Forestry Sciences, University of Palermo, Palermo, Sicily, Italy

Mulching is a common agricultural practice for the advantages it provides during cultivation. To reduce plastic residues in the soil, the use of bio-degradable films instead of plastic is desirable. Once buried in the soil, bio-degradable film undergoes degradation processes driven by abiotic and biotic factors such as the activity of soil microbes. The aim of this study was to select microbial strains whose enzymatic activities are able to speed up the degradation of innovative, biodegradable, cellulose-chitosan based films. To this end, 119 bacteria were isolated from compost, digestate, agricultural soil and the gut or casts of earthworms, and subsequently tested for their ability to break down two types of biodegradable film: that which had been enriched with nitrogen and phosphorus (+NP) and the unenriched control (-NP). The ability of the bacteria to accelerate the degradation of the films was strain dependent, and the degradation proceeded with different speed and degree. Of the 119 isolated bacteria, 46 strains were able to degrade the unenriched (-NP) film to a greater or lesser extent, with 20 of them able to break it down completely. With regard to the enriched (+NP) film, 10 strains were able to degrade it, with 6 strains being able to break it down completely. These figures include 8 strains that were able to degrade both the enriched and unenriched films. Four novel cellulose-chitosan degrader bacteria were selected and identified as Bacillus subtilis ACT-8, Bacillus spp. DL-A1-11 Pseudomonas spp. I1, and Staphylococcus warneri F7. These strains will be further studied to assess their activity at a mesocosm-scale trial. The novelty of this study is the identification of bacteria strains able to degrade cellulose-chitosan based films. This finding is a contribution to the common effort to reduce the presence of axenic residues in the environment, and it may have a positive impact on the sector considering the possibility of applying the strains in bioaugmentation practice.