Enzymatic Potential of Bacteria and Fungi Isolates from the Sewage Sludge Composting Process

• Main Authors: Tatiana Robledo-Mahón, Concepción Calvo, Elisabet Aranda
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Applied Sciences
• Subjects: bacteria; composting; enzymes; fungi; sewage sludge
• Online Access: https://www.mdpi.com/2076-3417/10/21/7763

The aim of this study was the isolation and characterisation of the fungi and bacteria during the composting process of sewage sludge under a semipermeable membrane system at full scale, in order to find isolates with enzymatic activities of biotechnological interest. A total of 40 fungi were isolated and enzymatically analysed. Fungal culture showed a predominance of members of Ascomycota and Basidiomycota division and some representatives of Mucoromycotina subdivision. Some noticeable fungi isolated during the mesophilic and thermophilic phase were <i>Aspergillus</i>, <i>Circinella,</i> and <i>Talaromyces</i>. During the maturation phase, some lignin modifying enzyme producers, like <i>Purpureocillium</i>, <i>Thielavia</i>, <i>Bjerkandera,</i> or <i>Dichotomyces</i>, were found. Within this group, <i>Thielavia</i> and <i>Bjerkandera</i> showed high activity with production of laccases and peroxidases. In the bacterial culturome, a total of 128 strains were selected and enzymatically analysed. Bacillales, Actinomycetales, Pseudomonadales, and Lactobacillales were the orders most represented in culture-bacteria. <i>Bacillus pumilus</i>, <i>B</i>. <i>stratosphericus</i>, <i>B</i>. <i>safensis,</i> and <i>Pseudomonas formosensis</i> were the species most efficient in enzyme production, particularly peroxidases, polyphenol oxidases ammonifying activity, and amylases. These results showed that sewage sludge composting piles could represent a source of microorganisms which have adapted to adverse conditions.