Using fungi to catch algae: Har­vest­ing microal­gae for fuels and chem­ic­als production

Waste bio­mass from fungal fer­ment­a­tion pro­cesses could be used to bind to and har­vest microal­gae being used in oth­er bio­tech­no­logy applic­a­tions. A*STAR research­ers have suc­cess­fully demon­strated this pro­ced­ure with fungal myceli­um — the main veget­at­ive part of a fungus such as the tangled mass of under­ground fibers beneath sprout­ing mush­rooms. Suit­able fungal bio­mass might be obtained cheaply or per­haps even freely to offer a sus­tain­able and envir­on­ment­ally sound meth­od for har­vest­ing microal­gae. The poten­tial uses of microal­gae include burn­ing their bio­mass as fuel or turn­ing them into mini-factor­ies for mak­ing biod­ies­el or spe­cif­ic chem­ic­als includ­ing lip­ids, sug­ars or drugs. ​“The lack of an eco­nom­ic and effect­ive meth­od for har­vest­ing microal­gae is one of the bot­tle­necks lim­it­ing their com­mer­cial use in bio­tech­no­logy,” explains Maha­bubur Taluk­der of the A*STAR Insti­tute of Chem­ic­al and Engin­eer­ing Sci­ences. Microal­gae can be cul­tured in a broth and exist­ing meth­ods for har­vest­ing them include cent­ri­fu­ga­tion or a pre­cip­it­a­tion pro­cess called floc­cu­la­tion using chem­ic­al treat­ments. All cur­rent meth­ods how­ever suf­fer sig­ni­fic­ant draw­backs, explains Taluk­der. For instance, cent­ri­fu­ga­tion is too expens­ive to be used for low value uses of microal­gae, such as bio­fuel. Sim­il­arly inad­equate, chem­ic­al floc­cu­la­tion con­tam­in­ates the har­ves­ted microal­gae with tox­ic met­al salts, caus­ing dif­fi­culties in fur­ther pro­cessing or extrac­tion of desired products. The A*STAR team knew that less tox­ic nat­ur­al mater­i­als such as starch could be used to pre­cip­it­ate and col­lect some fresh­wa­ter microal­gae, but this is not suit­able for mar­ine microal­gae due to undesir­able effects of the salty solu­tions. What is needed is a non-tox­ic and prefer­ably nat­ur­al and widely avail­able mater­i­al that can bind to, immob­il­ize and pre­cip­it­ate both fresh­wa­ter and mar­ine microal­gae. This led the research­ers to invest­ig­ate fungal myceli­um, which they found was not only effect­ive but could also add value by con­trib­ut­ing to the total bio­mass in the com­bined and har­ves­ted mater­i­al. The team screened sev­er­al vari­et­ies of fungi with vary­ing res­ults, in some cases achiev­ing a har­vest­ing effi­ciency of 97 per cent after sev­er­al hours of mech­an­ic­al mix­ing with four times the mass of wet myceli­um. Detailed ana­lys­is indic­ated that the key to the bind­ing and immob­il­iz­ing effect is a simple ion­ic attrac­tion between the dif­fer­ing elec­tric charges on the sur­face of the microal­gae and the fungal myceli­um. ​“The next step is to find a col­lab­or­at­or or indus­tri­al part­ner will­ing to invest in and fur­ther explore the inven­tion and com­mer­cial­ize it,” says Taluk­der, as his focus turns from the labor­at­ory toward the chal­lenges of scale-up and indus­tri­al pro­duc­tion.

Ori­gin­al publication:

Md. Maha­bubur Rah­man Taluk­der, Probir Das, Jin Chuan Wu. Immob­il­iz­a­tion of microal­gae on exo­gen­ous fungal myceli­um: A prom­ising sep­ar­a­tion meth­od to har­vest both mar­ine and fresh­wa­ter microal­gae. Bio­chem­ic­al Engin­eer­ing Journ­al, 2014; 91: 53 DOI: 10.1016/j.bej.2014.07.001 Source: Agency for Sci­ence, Tech­no­logy and Research (http://www.research.a‑star.edu.sg/research/7178)