Synergy of two thermophiles enables decomposition of poly-ɛ-caprolactone under composting conditions

Abstract

The ultimate degradation (i.e. complete mineralization) of biodegradable polymers proceeds through hydrolysis to the production of degradation intermediates (primary degradation) that are then taken into the microbial cell and further degraded to CO2 and water. We first isolated thermophilic actinomycete (Streptomyces thermonitrificans PDS‐1), which has the activity of ultimate degradability, from compost in which poly‐ɛ‐caprolactone (PCL) degraded vigorously. We next tried to investigate the detailed mechanisms of degradation of the PCL in compost by developing a new experimental method in which isolated microorganisms are used to inoculate sterilized compost raw materials containing PCL. It was confirmed that the ultimate degradation of PCL could not be achieved by the action of the strain PDS‐1 alone, and that a supplementary microorganism (Bacillus licheniformis HA1) isolated from compost utilizes the degradation intermediates and also increases the activity of the other primary microorganism (PDS‐1) by adjusting the pH. We could thus show experimental proof of synergy between two thermophiles in the ultimate degradation of a biodegradable polymer in compost.

Degradation of poly(ε-caprolactone) by a thermophilic bacterium Ralstonia sp. strain MRL-TL isolated from hot spring

“…It belongs to the class b-proteobacteria. The degradation of PCL has been studied by various researchers (Hirotsu et al, 2000;Khatiwala et al, 2008;Li et al, 2012) as well as under thermophilic conditions (Sanchez et al, 2000;Nakasaki et al, 2006;Tseng et al, 2007;Chua et al, 2013). However, there are limited reports on degradation of polyesters by thermophilic strain from genus Ralstonia as well as the depolymerases from Ralstonia sp.…”

Biodegradation of Wasted Bioplastics in Natural and Industrial Environments: A Review

“…As mentioned in Endres [29] "degradability is a functional property or a disposal option at the end of the material's life cycle". The degradation process depends on a combination of abiotic (UV, temperature, moisture, pH) and biotic processes and parameters (microbial activity) [19,26,33,38,112].…”

“…As already demonstrated, biodegradability depends on the chosen environment and it can differ from one environment to another [38]. So, the environmental conditions affect the rate of decomposition [29,112], as well as the test conditions used [111], and the type of the biodegradable polymer that is being examined [112] should be chosen properly. Most commonly examined degradation environments were aerobic, such as those of compost [127], which is a common waste treatment option.…”

Degradation of Poly(ε-caprolactone) by thermophilic Streptomyces thermoviolaceus subsp. thermoviolaceus 76T-2

“…Degradation of PCL may take place in soil, water, and compost by microorganisms (Tokiwa et al 1976, Nishida and Tokiwa 1993, Klingbeil et al 1996, Abou-Zeid et al 2001, Ponsart et al 2001, Federle et al 2002, Abou-Zeid et al 2004, Nakasaki et al 2006, Tokiwa et al 2009). Most PCL-degrading fungi are found in genera Penicillium and Aspergillus (Tokiwa et al 1976, Benedict et al 1983b, Sanchez et al 2000) , and most PCL-degrading bacteria belong to the genus Clostridium (Abou-Zeid et al 2001, 2004).…”

“…Most PCL-degrading fungi are found in genera Penicillium and Aspergillus (Tokiwa et al 1976, Benedict et al 1983b, Sanchez et al 2000) , and most PCL-degrading bacteria belong to the genus Clostridium (Abou-Zeid et al 2001, 2004). A thermophilic Streptomyces isolated from compost was found to have a higher PCL-degrading activity than thermotolerant Aspergillus (Nakasaki et al 2006). Since composting at high temperature is an ideal method for recycling biodegradable plastics by thermophilic microorganisms (Tokiwa et al 2009), isolation of thermal resistant PCL-degraders is desired.…”