Microbial advanced biofuels production: overcoming emulsification challenges for large-scale operation

Microbial cells as colloidal particles: Pickering oil-in-water emulsions stabilized by bacteria and yeast

“…This ability to reside at the petroleum hydrocarbon-water interface and stabilize O/W emulsions was also later reported (Dorobantu, Yeung, Foght, & Gray, 2004;Rosenberg & Rosenberg, 1985). More recently, microbial cells have been shown to stabilize O/W emulsions and produce biosurfactants during microbial production of fuels (Balat & Balat, 2010;Heeres, Picone, van der Wielen, Cunha, & Cuellar, 2014;Lim & Teong, 2010;Lin, Cunshan, Vittayapadung, Xiangqian, & Mingdong, 2011;Yusuf, Kamarudin, & Yaakub, 2011), resulting in emulsions resistant to heat treatments and extensive centrifugation (Furtado, Picone, Cuellar, & Cunha, A C C E P T E D M A N U S C R I P T…”

Bioprocess Engineering for Microbial Synthesis and Conversion of Isoprenoids

“…The formation of emulsions, although in some cases advantageous for creation of a large interfacial area, may create significant problems in separation of the organic phase for further product removal; furthermore, organic phase or cell recycling represents an important practical issue in downstream processing of industrial-scale bioprocesses [39]. Surface-active components, often produced by microorganisms themselves as a protective mechanism or to improve substrate availability, impede phase separation and promote the formation of stable emulsions.…”

“…In addition to those microorganism properties generally desirable from a bioprocess-oriented viewpoint, such as the ability to use low-cost feedstocks, tolerance to extreme conditions, or resistance to inhibitors, isoprenoid bioprocesses would benefit from biocatalysts with low-emulsion-forming tendency and tolerance against organic compounds. This would dramatically increase the ease of product recovery in aqueous-organic two-phase systems simply by gravity separation without the need for centrifugation or de-emulsification techniques which further raise process costs [39]. For price competitive "low-cost high-volume" products such as biofuels the possibility of operating a bioprocess in a continuous mode including the possibility of cell reuse is a valuable measure to increase productivity and lower capital cost [23].…”

An overview on biofuel and biochemical production by photosynthetic microorganisms with understanding of the metabolism and by metabolic engineering together with efficient cultivation and downstream processing

“…A better understanding on the mechanism of emulsion formation is necessary for the performance improvement based on nanotechnology as well as electrochemical properties such as ion, charge, viscosity, interface stabilization [207].…”