Qualitative Analysis of Microbial Dynamics during Anaerobic Digestion of Microalgal Biomass in a UASB Reactor

Abstract

Anaerobic digestion (AD) is a microbiologically coordinated process with dynamic relationships between bacterial players. Current understanding of dynamic changes in the bacterial composition during the AD process is incomplete. The objective of this research was to assess changes in bacterial community composition that coordinates with anaerobic codigestion of microalgal biomass cultivated on municipal wastewater. An upflow anaerobic sludge blanket reactor was used to achieve high rates of microalgae decomposition and biogas production. Samples of the sludge were collected throughout AD and extracted DNA was subjected to next-generation sequencing using methanogen mcrA gene specific and universal bacterial primers. Analysis of the data revealed that samples taken at different stages of AD had varying bacterial composition. A group consisting of Bacteroidales, Pseudomonadales, and Enterobacteriales was identified to be putatively responsible for the hydrolysis of microalgal biomass. The methanogenesis phase was dominated by Methanosarcina mazei. Results of observed changes in the composition of microbial communities during AD can be used as a road map to stimulate key bacterial species identified at each phase of AD to increase yield of biogas and rate of substrate decomposition. This research demonstrates a successful exploitation of methane production from microalgae without any biomass pretreatment.

Diversidade bacteriana associada à biodegradação de resíduos sólidos urbanos

“…Bactérias que degradam a matéria orgânica são sensíveis à presença de metais pesados, cujas concentrações são frequentemente encontradas em RSU, podendo prejudicar o processo biodegradativo. Liu et al (DOLOMAN et al, 2017;KLOCKE et al, 2007).…”

Augmentation of Granular Anaerobic Sludge with Algalytic Bacteria Enhances Methane Production from Microalgal Biomass

“…Bacterial enrichments to isolate potential algalytic bacteria to be used in bioaugmentation were performed on anaerobic sludge from up flow anaerobic sludge blanket (UASB) reactors seeded with anaerobic sediments from the Logan City Wastewater Lagoons (LCWL), Utah [11,12]. Microalgal biomass collected from the surface of the LCWL was supplied to the reactor as a substrate for microbial growth and biogas production.…”

“…The fed biomass was a mixed culture, comprised primarily of Chlorella, Chlorococcum, Chlamydomonas, Scenedesmus, Synedra, Navicula, Schroderia, Euglena, Coelastrum, and members of nonheterocystous cyanobacteria. Samples from the reactor sludge bed were collected on the 20th day after the start of anaerobic digestion, which is the time predicted when AD would be in the hydrolytic phase [11].…”

“…Isolated bacteria were expected to have a general fermentative behavior and, thus, two types of microbiological media were chosen for isolation of pure cultures: general medium for fermentative microorganisms, such as Tryptic Soy Broth (TSB), and a Grant and Holt (GH) media specific to the most abundant type of bacterium identified for the hydrolysis stage (Pseudomonas spp. [11,14]). A series of both liquid and agar media were used to isolate pure strains of potentially algalytic bacteria.…”

“…Members of Calditrichaeota and Actinobacteria phyla can also be acting as secondary fermenters, after the initial lysis of the algal biomass was already performed by the augmenting bacterial mixture. A follow-up study will be to repeat the experiment but have granules withdrawn from the reactors at different time points throughout the digestion, to compare the microbial population at different stages of anaerobic digestion (hydrolysis, acidogenesis, and methanogenesis) [11].…”