NOVELTY - Mesoporous particle comprises (a) ordered porous silicon oxide matrix with hexagonal symmetry, and dialkylimidazolium groups covalently bonded to the outside surface through a silicon-carbon bond, (b) ordered porous silicon oxide matrix with hexagonal symmetry, 10-20C alkyl groups covalently bonded to the outside surface of the mesoporous particle, and aminoalkyl groups covalently bonded to the inner surfaces of pores of the mesoporous particle, where the alkyl is 1-12C alkyl, or (c) ordered tetragonal mesoporous carbon matrix with several pores.    USE - The mesoporous particle is useful for selective sequestration of free fatty acids, preferably stearic acid, oleic acid, linoleic acid, palmitic acid and palmitoleic acid, and selective extraction of organic compounds, preferably mono-, di- or tri-glycerides, fatty acids, polar lipids, and their combinations, from microorganisms, preferably algae chosen from Botryococcus, Chlorella, Neochloris, Nannochloropsis and genetically modified species (all claimed). The obtained free fatty acids are used for producing biodiesel.    ADVANTAGE - The mesoporous particles extract large amount of fatty acids eco-friendly, inexpensively and rapidly from genetically modified algae compared to wild-type algae. The mesoporous particle does not affect algae and thus the algae are used for repeating the process. The method (M2) does not require further purification process to remove contaminants including sterols, chlorophyll, tocopherols and terpenes.    DETAILED DESCRIPTION - Mesoporous particle comprises (a) ordered porous silicon oxide matrix with hexagonal symmetry, and dialkylimidazolium groups covalently bonded to the outside surface through a silicon-carbon bond, where the diameter of particle is 75-125 nm, (b) ordered porous silicon oxide matrix with hexagonal symmetry, 10-20C alkyl groups covalently bonded to the outside surface of the mesoporous particle, and aminoalkyl groups covalently bonded to the inner surface of pores of the mesoporous particle, where the alkyl is 1-12C alkyl and is optionally interrupted by one or two amino groups, and has two different average pore size distributions of 3-5 nm and 13-15 nm, respectively, or (c) ordered tetragonal mesoporous carbon matrix with several pores, where the particle is spheroid and has diameter of 50-250 nm and surface area of 1800-2200 m2/g, and the pores have average diameter of 2-3 nm. INDEPENDENT CLAIMS are included for the following:    (1) selective (M1) sequestration of free fatty acids from microorganisms that produce free fatty acids, involves contacting the microorganisms with several particles, and selectively absorbing or adsorbing the free fatty acids to the pores or surface of the particles, where less than 20 wt.% of the compounds adsorbed or absorbed by the particles are compounds other than free fatty acids;    (2) selective (M2) extraction of organic compounds from microorganism, involves contacting a microorganism in presence of a medium comprising water, with a hydrophobic organic solvent, to form a first mixture, contacting the first mixture with several mesoporous particles or non-functionalized mesoporous silica particles, to form a second mixture in which the mesoporous particles sequester the organic compounds from the microorganism, isolating the mesoporous particles from the second mixture and removing the organic compounds from the mesoporous particles to obtain a group of selectively extracted organic compounds; and    (3) matrix for mass spectrometry analysis, comprising mesoporous particles isolated from the second mixture of the method (M2).