The main area in our lab is the production of a variety of biofuel and biochemicals from microalgal biomass involving biomass hydrolysis, microbial fermentation, and bioproducts separation. Another area is macroalgal biomass utilization technology. Bio-shift reaction to produce hydrogen from carbon monooxide is also included in our research scope.
Microalgal biomass utilization based on molecular management concept: Defatted or intact microalgal biomass was hydrolyzed by using a liquid and/or solid acid catalyst releasing up to 8 different monosugars of glucose, galactose, mannose, rhamnose, fucose, xylose, ribose and arabinose. The production of bioproducts by fermentation using such multi-sugar mixture showed much more complex chemistry than one based on a monosugar, most commonly, glucose. When Nannochloropsis oceanica, for example, was hydrolyzed, 7 monosugars mentioned above except arabinose were produced. The sugar mixture was successfully used as carbon source for the production of ethanol and DagA, an agarase, by using Saccharomyces cerevisiae and Streptomyces lividans in sequence. The sugar mixture was also used for 2,3-butanediol production by Klebsiella oxitoca. In both cases, fucose was never metabolized or consumed extreme slowly, being the only unconsumed sugar in the resulting fermentation broth. Fucose is a very high value-added compound with potential applications as active ingredient for anti-aging products, inducer of long-term potentiation of memory, and allergic contact dermatitis suppressant, etc. A simulated moving bed chromatography process for the separation is under development in cooperation with Prof. Sung Yong Mun’s laboratory at Hanyang University, Seoul.
Macroalgal biomass utilization: Agarose, the main component of red algae galactan, was chemically hydrolyzed by using acid with the formation of galactose, 5- hydroxymethylfurfural, and levulinic acid. These 3 compounds were successfully separated by nanofiltration and electrodialysis. A two-stage enzymatic process was also developed for agarose hydrolysis. In the first stage, a mixture of two different agarases, AgaG1 and DagB, was used to produce neoagarobiose from agarose. In the second stage, a neoagarobiose hydrolase was used to hydrolyze neoagarobiose into galactose and anhydrogalactose. The resulting crude galactose solution was used for ethanol production by yeast to demonstrate its potential as carbon source for fermentation. A process for enzymatic hydrolysis of agarose by using DagA is under development to produce neoagarotetraose and neoagarohexaose, which have a number of health benefits.
Biohydrogen Production: A bubble column bioreactor is under development for the production of hydrogen by Thermococcus onnurineus NA1 from carbon monoxide.