Dennis J. Miller

Efficient ethanol production from brown macroalgae sugars by a synthetic yeast platform

The increasing demands placed on natural resources for fuel and food production require that we explore the use of efficient, sustainable feedstocks such as brown macroalgae. The full potential of brown macroalgae as feedstocks for commercial-scale fuel ethanol production, however, requires extensive re-engineering of the alginate and mannitol catabolic pathways in the standard industrial microbe Saccharomyces cerevisiae. Here we present the discovery of an alginate monomer (4-deoxy-l-erythro-5-hexoseulose uronate, or DEHU) transporter from the alginolytic eukaryote Asteromyces cruciatus. The genomic integration and overexpression of the gene encoding this transporter, together with the necessary bacterial alginate and deregulated native mannitol catabolism genes, conferred the ability of an S. cerevisiae strain to efficiently metabolize DEHU and mannitol. When this platform was further adapted to grow on mannitol and DEHU under anaerobic conditions, it was capable of ethanol fermentation from mannitol and DEHU, achieving titres of 4.6% (v/v) (36.2 g l−1) and yields up to 83% of the maximum theoretical yield from consumed sugars. These results show that all major sugars in brown macroalgae can be used as feedstocks for biofuels and value-added renewable chemicals in a manner that is comparable to traditional arable-land-based feedstocks.

Activated carbon from cherry stones

Fruit stones constitute a significant waste disposal problem for the fruit-processing industry. High-quality activated carbon can be produced from waste cherry stones: the activated carbon is low in impurities and has an adsorption capacity that compares favorably with commercial activated carbons. Activation at 800°C in steam for 2–3 hours, following initial carbonization, produces an activated carbon in about 10% yield (by weight) of the initial cherry stone. The activated carbons produced have surface areas (CO2 adsorption) as high as 1200 m2/g and CCl4 numbers of 70–80. Activation in carbon dioxide requires higher temperatures (900°C) and gives a carbon of slightly lower activity. Carbon from the hull, or hard outer portion of the fruit stone, provides essentially all of the adsorption capacity; the inner kernel does not form a microporous material. The hull structure is dominated by 0.4-micron pores which facilitate access to internal microporosity. This structure requires that the carbon be ground to less than 75 micron particles to achieve reasonable adsorption rates.

Role of oxygen surface groups in catalysis of hydrogasification of carbon black by potassium carbonate

The reaction rates of a nonporous graphitic carbon lampblack with hydrogen gas at 865°C and 500 psi were measured following treatments such as degassing and/or oxidation with and without impregnation of K2CO3. The results lead to the conclusion that oxygen surface groups enhance the reactivity of the carbon by generating “nascent” active sites on decomposition into CO and CO2. In the catalyzed case the basic and CO carbonyl groups form active and stable surface complexes. The acidic groups, on the other hand, could not be well characterized and may form stable and inactive or unstable and active complexes depending on their nature.

Butyric acid esterification kinetics over Amberlyst solid acid catalysts: the effect of alcohol carbon chain length.

The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid.

A novel process for recovery of fermentation-derived succinic acid: Process design and economic analysis

Recovery and purification of organic acids produced in fermentation constitutes a significant fraction of total production cost. In this paper, the design and economic analysis of a process to recover succinic acid (SA) via dissolution and acidification of succinate salts in ethanol, followed by reactive distillation to form succinate esters, is presented. Process simulation was performed for a range of plant capacities (13-55 million kg/yr SA) and SA fermentation titers (50-100 kg/m(3)). Economics were evaluated for a recovery system installed within an existing fermentation facility producing succinate salts at a cost of

Hydrogen gasification of HNO3-oxidized carbons

0.66/kg SA. For a SA processing capacity of 54.9 million kg/yr and a titer of 100 kg/m(3) SA, the model predicts a capital investment of

A kinetic model of the Amberlyst-15 catalyzed transesterification of methyl stearate with n-butanol

75 million and a net processing cost of

A mild approach for bio-oil stabilization and upgrading: electrocatalytic hydrogenation using ruthenium supported on activated carbon cloth

1.85 per kg SA. Required selling price of diethyl succinate for a 30% annual return on investment is

Electrocatalytic upgrading of model lignin monomers with earth abundant metal electrodes

1.57 per kg.

Effect of oxidation and other treatments on hydrogasification rate of coal char

Abstract The oxidation of carbon prior to hydrogen gasification as a means of enhancing methane formation rate is investigated. Carbon is oxidized by HNO 3 and gasified in hydrogen in a high-pressure differential reactor. Samples are analyzed by x-ray photoelectron spectroscopy (XPS) for surface oxygen content before and after pretreatment and reaction. Results for uncatalyzed gasification show a correlation between initial surface oxygen content and hydrogasification rate, but XPS results reveal that essentially no oxygen is present on the carbon surface during hydrogen gasification. This indicates that desorption of oxygen groups from the carbon surface generates reactive sites at which hydrogen gasification occurs. These nascent sites arise from acidic oxygen groups both fixed during oxidation and from oxygen in bulk carbon. In potassium carbonate-catalyzed hydrogen gasification, oxidation enhances the catalyzed rate as much as threefold. The catalyst interacts with basic oxygen groups on carbon to form reactive sites which are formed and regenerated continuously during gasification. Analysis by XPS shows that substantial oxygen and potassium are present on the carbon surface during hydrogen gasification; at high catalyst loadings and 725°C the Cls peak shows both carbonate groups and singly bound oxygen-carbon groups tentatively assigned as M—O—C.