Bacterial Community Structure and Biochemical Changes Associated With Composting of Lignocellulosic Oil Palm Empty Fruit Bunch

Abstract

Bacterial community structure and biochemical changes during the composting of lignocellulosic oil palm empty bunch (EFB) and palm oil mill effluent (POME) anaerobic sludge were studied by examining the succession of the bacterial community and its association with changes in lignocellulosic components by denaturing gradient gel electrophoresis (DGGE) and the 16S rRNA gene clone library. During composting, a major reduction in cellulose after 10 days from 50% to 19% and the carbon content from 44% to 27% towards the end of the 40-day composting period were observed. The C/N ratio also decreased. A drastic change in the bacterial community structure and diversity throughout the composting process was clearly observed using PCR-DGGE banding patterns. The bacterial community drastically shifted between the thermophilic and maturing stages. 16s rRNA clones belonging to the genera Bacillus, Exiguobacterium, Desemzia, and Planococcus were the dominant groups throughout composting. The species closely related to Solibacillus silvestris were found to be major contributors to changes in the lignocellulosic component. Clones identified as Thermobacillus xylanilyticus, Brachybacterium faecium, Cellulosimicrobium cellulans, Cellulomonas sp., and Thermobifida fusca, which are known to be lignocellulosic-degrading bacteria, were also detected and are believed to support the lignocellulose degradation.

Microbial community structure and dynamics in thermophilic composting viewed through metagenomics and metatranscriptomics

“…Analysis of the bacterial community structure at the levels of phylum and order by shotgun DNA as well as by 16S rRNA gene amplicon sequencing yields two main results: 1) shotgun DNA and 16S amplicon results by and large agree with each other; 2) the phyla and orders that are most abundant agree with those found in previous studies14789101112. The four most abundant phyla throughout the composting process are Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria (Supplementary Fig.…”

“…The biological decomposition of organic matter is performed by mesophilic and thermophilic microbial consortia with distinct physiological requirements and tolerances, consistent with the continuously changing environment throughout composting34567. Bacterial phyla including Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria are routinely found in composting, being more or less abundant depending on the starting materials and the composting procedure14789101112. Generally, fungi are not detected in composting piles above 65 °C, suggesting that their degradative activities during the thermophilic stages of composting are minor compared to that of bacteria1314.…”

Periodic addition of anaerobic sludge enhanced the lignocellulosic degradation rate during co-composting of oil palm biomass

“…The results suggested that the highest value for degradation rate, OM loss and lowest final C/N were obtained by using periodic addition of sludge compared to the addition of only water and no addition at all regardless of the initial C/N ratio of the different experiments. The results obtained agreed with those of the previous work carried out by Mohd Zainudin et al (2014) and Wan Razali et al (2012). Clearly, as expected, periodic addition of sludge allowed the organic matter loss increase to justify addition not only for moisture content regulator but supporting nutrient needs for microbial to grow.…”

Temporal dynamics and ecophysiology of thermophilic composting analyzed through metagenome-assembled genomes

“…In spite of all this potential, knowledge on how to control and explore those microbes and their functions remains encrypted within their genomes and the multiple combinations of metabolic pathways that they can activate [7][8][9]. So far, research on composting microbes has focused mainly on enriched cultures [9][10][11] or taxonomic biodiversity assessments based on 16S rRNA gene amplicon sequencing data [12,13]. Enriched cultures have lower diversity richness due to cultivation bias and the limited number ecological niches [9].…”