Lenny B. Malihan

Brown algae hydrolysis in 1-n-butyl-3-methylimidazolium chloride with mineral acid catalyst system.

The amenability of three brown algal species, Sargassum fulvellum, Laminaria japonica and Undaria pinnatifida, to hydrolysis were investigated using the ionic liquid (IL), 1-n-butyl-3-methylimidazolium chloride ([BMIM]Cl). Compositional analyses of the brown algae reveal that sufficient amounts of sugars (15.5-29.4 wt.%) can be recovered. Results from hydrolysis experiments show that careful selection of the type of mineral acid as catalyst and control of acid loading could maximize the recovery of sugars. Optimal reaction time and temperature were determined from the kinetic studies on the sequential reducing sugar (TRS) formation and degradation. Optimal reaction times were determined based on the extent of furfurals formation as TRS degradation products. X-ray diffraction and environmental scanning electron microscopy confirmed the suitability of [BMIM]Cl as solvent for the hydrolysis of the three brown algae. Overall results show the potential of brown algae as renewable energy resources for the production of valuable chemicals and biofuels.

Metal-free mild oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

The potential of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-hydroxy-TEMPO radical) as an oxidant with [bis(acetoxy)-iodo]benzene (BAIB) and acetic acid (CH3COOH) as co-oxidants to convert 5-hydroxymethylfurfural (5-HMF) into 2,5-diformylfuran (2,5-DFF) was investigated. The effects of oxidant/acid dosages, choice of appropriate solvent, reaction temperature and time were determined to maximize the 2,5-DFF yield. Optimally, 66% 2,5-DFF yield was achieved in TEMPO/BAIB/CH3COOH system at 30 °C after 45 min in ethyl acetate. The reaction system is environmentally benign (metal-free) and energy efficient (mild at short reaction period). With scarce reports on 2,5-DFF production, the developed system provides an alternative route for a better access and wider application of this important platform chemical.

One-pot synthesis of 2,5-diformylfuran from fructose using a magnetic bi-functional catalyst

A magnetic bi-functional WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst was prepared to directly synthesize 2,5-diformylfuran (2,5-DFF) from fructose. The chlorosilylated SiO2@Fe3O4 (Cl-SiO2@Fe3O4) nanoparticles served as the platform for the two functionalities. Tungstic acid was generated via protonation of sodium tungstate, which was directly attached on the platform via nucleophilic –Cl displacement. Meanwhile, oxovanadium was complexed with a salten ligand which was functionalized on the Cl-SiO2@Fe3O4. Characterization results confirmed the successful preparation of the WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst. Under the optimal one-pot system, tungstic acid-mediated fructose dehydration afforded 82% 5-hydroxymethylfurfural (5-HMF) in 1 h. Upon co-oxidant H2O2 addition, in situ 5-HMF oxidation by the activated oxoperoxovanadium species produced 71% of 2,5-DFF after 15 h under ambient air. The stability of 5-HMF formation was found critical to 2,5-DFF production. Aside from the catalytic efficiency and process simplicity, the WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst was readily retrieved magnetically and re-used multiple times with marginal losses in its activity.

SBA-15 supported ionic liquid phase (SILP) with H2PW12O40− for the hydrolytic catalysis of red macroalgal biomass to sugars

A supported ionic liquid phase (SILP) catalyst for biomass hydrolysis was prepared via immobilization of an acidic ionic liquid (IL) with a phosphotungstic counter-anion H2PW12O40− (HPW) on ordered mesoporous silica (SBA-15). Characterization results from XRD, N2 physisorption, FT-IR, TGA and SEM/TEM image analyses confirmed the successful preparation of the SILP catalyst (SBA-IL–HPW). Meanwhile, its catalytic performance was evaluated in terms of sugar production from the hydrolysis of different biomasses in water. Under optimal hydrolysis conditions, SBA-IL–HPW yielded 73% D-galactose from agarose and 58% D-glucose from cellobiose. Moreover, SBA-IL–HPW effectively hydrolyzed the red macroalgae G. amansii as it afforded 55% total reducing sugar and 38% D-galactose yields. SBA-IL–HPW was easily separated from the hydrolysates after reaction and was re-used five times without significant loss of activity. Overall findings reveal the potential of SBA-IL–HPW as a durable, environmentally benign catalyst for sugar production from renewable resources.

Metabolic engineering of Escherichia coli for biosynthesis of d-galactonate

Abstractd-galactose is an attractive substrate for bioconversion. Herein, Escherichia coli was metabolically engineered to convert d-galactose into d-galactonate, a valuable compound in the polymer and cosmetic industries. d-galactonate productions by engineered E. coli strains were observed in shake flask cultivations containing 2xa0gxa0L−1d-galactose. Engineered E. coli expressing gld coding for galactose dehydrogenase from Pseudomonas syringae was able to produce 0.17xa0gxa0L−1d-galactonate. Inherent metabolic pathways for assimilating both d-galactose and d-galactonate were blocked to enhance the production of d-galactonate. This approach finally led to a 7.3-fold increase with d-galactonate concentration of 1.24xa0gxa0L−1 and yield of 62.0xa0%. Batch fermentation in 20xa0gxa0L−1d-galactose of E. coli ∆galK∆dgoK mutant expressing the gld resulted in 17.6xa0gxa0L−1 of d-galactonate accumulation and highest yield of 88.1xa0%. Metabolic engineering strategy developed in this study could be useful for industrial production of d-galactonate.