Monitoring of Air Microbial Contaminations in Different Bioenergy Facilities Using Cultural and Biomolecular Methods

Abstract

Bioaerosol exposure linked to the bioenergy production from waste and its effects on human health in occupational and residential environments has rising interest nowadays. The health risk associated with the exposure includes mainly infective diseases, allergies, chronic bronchitis, and obstructive pulmonary disease. A risk assessment's critical point is the bioaerosol quality and quantity characterization. The aim of this study is to evaluate the application of different methods for the analysis of bioaerosol sampled in bioenergy plants. This study involved six Italian plants for the treatment of biomasses and energy production. Bioaerosol cultural evaluation was performed, by Surface Air System (SAS) sampler, and DNA was extracted from PM0.49 samples and Low Melting Agar plates. qRT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and band sequencings were performed. The cultural method is able to detect less than 15% of what is evaluable with bio-molecular methods. A low sample alfa-diversity and a high beta-biodiversity in relation to feedstock and process were observed. Sequencing showed microorganisms with a hygienic-sanitary relevance such as Arcobacter, Pseudomonas, Enterobacter, Klebsiella, Enterococcus and Bacillus. Integrated cultural and biomolecular methods can be more exhaustive to evaluate bioaerosol's exposure in the occupational environment.

Keywords: PCR-DGGE; bioaerosol; bioenergy production; microbial pollution; qRT-PCR.

Figure 1

Boxplot of bacterial quantification methods for each plant type. Legend: cultural count represents the total mesophilic cultural count (37 °C, UFC/m³), count from LMA represents the biomolecular quantification with DNA extracted from LMA plates (copies/m³) and count from filters represents the biomolecular quantification with DNA extracted from filter (copies/m³).

Figure 2

Phylogenetic analysis, bacteria dendrogram of samples. Pearson similarity coefficients are reported near the node. Colour legend: green (organic fraction of municipal solid waste (OFMSW)), yellow (agricultural and livestock biomasses (ALB)), red (wastewater treatment sludge (WWTS)), and violet (lignocellulosic biomasses (LCB)). Replicate samples (i.e., 1-1bis-1ter-1quater) are also reported. Whenever -ter and -quarter replicates are present, those are from LMA samples.

Figure 3

Boxplot of biodiversity Shannon’s indices in relation to the type of plant investigated.