Assessment of bacterial degradation of lignocellulosic residues (sawdust) in a tropical estuarine microcosm using improvised floating raft equipment

• Lignocellulose-degrading bacterial species were identified by 16Sr RNA gene sequencing.
• Bioremoval of lignin was up to 83% at the rate 1.80 × 10−5 g d−1 cm−3.
• Level of degradation is higher under in situ, as compared to laboratory condition.

In situ and laboratory studies were carried out to determine the ability of bacterial strains isolated from a tropical lagoon to degrade lignin and carbohydrate components of sawdust, with a view to abating the impact of sawdust pollution on these ecosystem. A floating raft system was designed and fabricated to carry out the in situ biodegradation studies over a period of 24 weeks. Nine bacterial strains identified by 16S rRNA gene sequencing as species of Streptomyces, Bacillus and Paenibacillus isolated from the lagoon were used as seed organisms. In the in situ study, 59.2% of sawdust was depleted at the rate of 1.175 × 10−4 g d−1 cm−3 by the bacterial isolates, whereas the lignin component of the sawdust decreased by up to 82.5% at the rate of 1.80 × 10−5 g d−1 cm−3. The maximum decrease in carbohydrate content was 85% at the rate of 2.192 × 10−7 g d−1 cm−3. In a similar experiment under laboratory conditions, total weight losses ranging from 26 to 51% in the wood residues were observed.