Bacterial Lysis of Microalgal Cells

Abstract

This short communication reports a pioneering research of using bacteria for simultaneous algal cell disruption and cell wall/membrane utilization. Microalgae are regarded as one of the most promising feedstock that can potentially address the twin challenges of energy security and environmental protection due to their fast growth rate, high lipid content and CO 2 biofixation capabilities. However, different from their terrestrial oil crops, the extracellular coverings of algae vary significantly, ranging from multiple layers of elaborate scales to highly mineralized coats to complex cell walls consisting of structural fibrils enmeshed in complex matrices. These strong cellular walls and membranes are resistant to disintegration, which makes lipid extraction from microalgae difficult. A bacteria-assisted algal cell disruption and lipid extraction method was studied here. The bacteria Sagittula stellata showed strong algicidal activity against two microalgae, Nannochloropsis oculata and Dunaliella salina. The algicidal rate reached 64.7% on N. oculata and 52.4% on D. salina in six days. A decrease in chlorophyll-a fluorescence density of both algae and bacteria addition was also observed. After 6-day treatment by S. stellata, hexane-extracted crude lipid contents increased from 32.9% to 45.7% and from 19.6% to 36.4% for N. oculata and D. salina, respectively, when compared with no bacterial addition. The preliminary results concluded that S. stellata was effective in the lysis of microalgal cells for effective lipid recovery.

Algicidal microorganisms and secreted algicides: New tools to induce microalgal cell disruption

“…By employing this biological treatment for the production of biofuels, alga-lytic microorganisms assist the degradation of algal cell structure and improve the accessibility to intracellular macromolecules (such as lipids or carbohydrates). Lipid extraction is markedly enhanced in comparison to the same extraction without this biological treatment Lenneman et al 2014;Wang and Yuan 2014). For biogas production, biological treatment could act as coupled cell disruption and cell degradation treatment, resulting in the release of a higher content of organic matter than processes which do not utilize biological treatment.…”

“…They have been collected from the natural environment of marine microalgae in order to reach cell lysis in saline conditions (Lenneman et al 2014, Matsumuto et al 2003Muñoz et al 2014) or isolated from heterogeneous environmental samples recovered in contaminated open ponds or shallow marsh sediments (Lenneman et al 2014). Cellulolytic bacteria were also isolated from digestive guts of algae predators such as filter-feeding bivalve mollusks (Muñoz et al 2014), and from lignin-rich, pulp mill effluent (Wang and Yuan 2014). Specific microalgae cell wall damage showed evidence of the effectiveness of biological treatment (Afi et al 1996;Chen et al 2013;Lenneman et al 2014;Lü et al 2013).…”

“…Furthermore, mutualistic and allelopathic interaction between bacteria and microalgae have recently been highlighted for applications in biofuels production processes as a potential strategy to control culture contamination during algal cultivation (Bacellar Mendes and Vermelho 2013), to fast-sedimentation of microalgae by bacterial aggregation and to disrupt microalgae biomass using algicidal microorganisms Cheng et al 2013;Lenneman et al 2014;Lü et al 2013;Muñoz et al 2014;Wang and Yuan 2014).…”

“…Microalgal degradation by microorganisms is a disruption approach for biofuels production processes that is considered cost-effective compared to the traditional mechanical and chemical cell disruption methods, since it is cheaper and simpler than the external addition of enzymes, as enzymes do not require extraction or purification Lenneman et al 2014;Lü et al 2013;Muñoz et al 2014;Wang and Yuan 2014). However, a drawback of this system is that degrading microorganisms must be chosen carefully to secrete strain-specific compounds and the dosage between microorganism inoculum and algal biomass needs to be optimized to reach an efficient lysis.…”

Biotechnologies for bulk production of microalgal biomass: from mass cultivation to dried biomass acquisition

“… Secreted metabolites 45.6% (1 d) [ 112 ] Enterobacter cloacae , Gibberella moniliformis C. pyrenoidosa n/d n/d [ 113 ] Bowmanella denitrificans C. vulgaris Secreted metabolites 28.7% [ 114 ] Bacillus thuringiensis ITRI-G1 C. vulgaris Secreted AES-Bt agents 100% (8 h) [ 115 ] Microbacterium paraoxydans C. vulgaris Secreted atrazine-desethyl 64.38% [ 116 ] Ponticoccus sp. CBA02 D. salina Secreted metabolites n/d [ 117 ] Sagittula stellata D. salina n/d 52.4% (6 d) [ 118 ] Paenibacillus polymyxa MEZ6 H. pluvialis Secreted metabolites 46.3% [ 119 ] Other algae Oocystis sp. Arthrospira sp.…”