Use of Cellulolytic Marine Bacteria for Enzymatic Pretreatment in Microalgal Biogas Production

Abstract

In this study, we designed and evaluated a microalgal pretreatment method using cellulolytic bacteria that naturally degrades microalgae in their native habitat. Bacterial strains were isolated from each of two mollusk species in a medium containing 1% carboxymethyl cellulose agar. We selected nine bacterial strains that had endoglucanase activity: five strains from Mytilus chilensis, a Chilean mussel, and four strains from Mesodesma donacium, a clam found in the Southern Pacific. These strains were identified phylogenetically as belonging to the genera Aeromonas, Pseudomonas, Chryseobacterium, and Raoultella. The cellulase-producing capacities of these strains were characterized, and the degradation of cell walls in Botryococcus braunii and Nannochloropsis gaditana was tested with "whole-cell" cellulolytic experiments. Aeromonas bivalvium MA2, Raoultella ornithinolytica MA5, and Aeromonas salmonicida MC25 degraded B. braunii, and R. ornithinolytica MC3 and MA5 degraded N. gaditana. In addition, N. gaditana was pretreated with R. ornithinolytica strains MC3 and MA5 and was then subjected to an anaerobic digestion process, which increased the yield of methane by 140.32% and 158.68%, respectively, over that from nonpretreated microalgae. Therefore, a "whole-cell" cellulolytic pretreatment can increase the performance and efficiency of biogas production.

Gut content microbiota of introduced bigheaded carps ( Hypophthalmichthys spp.) inhabiting the largest shallow lake in Central Europe

“…Members of the genus Aeromonas were present in the foregut samples with a mean relative abundance of about 11% (based on pyrosequencing data), and several species from this genus produce cellulase enzyme (Jiang et al, 2011;Muñoz et al, 2014). Moreover, the genera Holdemania (Mishra et al, 2013) and Macellibacteroides (Jabari et al, 2012) were present in the hindguts (with 4% and 1% relative abundance, respectively), and these taxa are able to decompose cellulose-and hemicellulose-derived sugars (e.g.…”

Improving biogas production from microalgae by enzymatic pretreatment

“…Furthermore, the pretreatment effect and economic cost may be improved by replacing commercial enzymes by cellulolytic bacteria and fungi from terrestrial environments. Recent studies have shown that anaerobic digestion is improved by using natural enzymes from compost, ruminant faeces or vegetable waste (Muñoz et al, 2014;Prajapati et al, 2015). In this context, prospective research should investigate the effect of enzymatic pretreatment using continuous anaerobic reactors in order to estimate the energy balance and economic cost of the process, which is yet to be determined.…”

Microalgae as Future Fuel: Real Opportunities and Challenges

“…In enzymatic pretreatment cellulases and lipases are generally used. Enhanced biogas production was achieved when Botryococcus braunii and Nannochloropsis gaditana were pretreated with bacterial strains having endoglucanase/amylase and cellulase activity [83].…”