Biotechnological approach for the reduction of VOC in oriented strand boards

Abstract

Aldehydes and especially terpenes are among the most frequently emitted volatile organic compounds (VOC) in the wood processing industry. Wood products made of pine wood might influence humans well-being and the indoor environment because of the classification of VOC as irritants. Therefore, the actual study presents a biotechnological approach for the reduction of aldehydes and particularly the three major terpenes in pine wood, -pinene, -pinene and 3-carene, to obtain emission-reduced Oriented Strand Boards (OSB). The starting point of the study was the selection of bacterial strains based on their ability to metabolise -pinene as single carbon source in liquid culture. Pseudomonas putida and Pseudomonas fluorescens showed the best results and were therefore adapted and applied for further tests on pine wood particles and strands at laboratory scale, in which the wood samples were incubated with bacterial strains for 72 h at room temperature. Residual emissions were analysed by means of GC-MS. The most promising results were obtained with a mixture of both Pseudomonas strains, and after various optimization steps the experiments were stepwise enlarged towards technical scale. To address the requirements of industrial OSB production, the focus was laid on the reduction of incubation time at consistent degradation rates. OSB were then manufactured from the microbially treated pine wood strands. The microorganisms caused a distinct reduction of -pinene and -pinene in manufactured OSB within 48 h and even 24 h incubation time. A successful degradation of 3-carene in both, liquid culture and pine wood, was achieved by an optimised culture of the ascomycete Penicillium nigricans. This approach successfully solved the problem that the Pseudomonas strains efficiently degraded aldehydes and pinenes, but were unable to metabolise 3-carene. By merging fungus and bacteria, all of the three major terpenes were reduced within OSB, indicating that there were no antagonistic effects between the species. In the course of the research, the fungal enzyme laccase in the presence of a redox mediator system turned out to be very efficient in 3-carene conversion into non-volatile oxidation products under laboratory conditions. Moreover, a mixture of bacteria and laccase showed good results in terms of 3-carene reduction in pine wood particles. Collectively, the results of the present study revealed the potential of biotechnology for reducing potentially harmful terpene emissions from wood products.