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.

Microbiota associated with tubes of Escarpia sp. from cold seeps in the southwestern Atlantic Ocean constitutes a community distinct from that of surrounding marine sediment and water.

As the depth increases and the light fades in oceanic cold seeps, a variety of chemosynthetic-based benthic communities arise. Previous assessments reported polychaete annelids belonging to the family Siboglinidae as part of the fauna at cold seeps, with the 'Vestimentifera' clade containing specialists that depend on microbial chemosynthetic endosymbionts for nutrition. Little information exists concerning the microbiota of the external portion of the vestimentiferan trunk wall. We employed 16S rDNA-based metabarcoding to describe the external microbiota of the chitin tubes from the vestimentiferan Escarpia collected from a chemosynthetic community in a cold seep area at the southwestern Atlantic Ocean. The most abundant operational taxonomic unit (OTU) belonged to the family Pirellulaceae (phylum Planctomycetes), and the second most abundant OTU belonged to the order Methylococcales (phylum Proteobacteria), composing an average of 21.1 and 15.4% of the total reads on tubes, respectively. These frequencies contrasted with those from the surrounding environment (sediment and water), where they represent no more than 0.1% of the total reads each. Moreover, some taxa with lower abundances were detected only in Escarpia tube walls. These data constitute on the first report of an epibiont microbial community found in close association with external surface of a cold-seep metazoan, Escarpia sp., from a chemosynthetic community in the southwestern Atlantic Ocean.

Gas hydrate dissociation linked to contemporary ocean warming in the southern hemisphere.

Ocean warming related to climate change has been proposed to cause the dissociation of gas hydrate deposits and methane leakage on the seafloor. This process occurs in places where the edge of the gas hydrate stability zone in sediments meets the overlying warmer oceans in upper slope settings. Here we present new evidence based on the analysis of a large multi-disciplinary and multi-scale dataset from such a location in the western South Atlantic, which records massive gas release to the ocean. The results provide a unique opportunity to examine ocean-hydrate interactions over millennial and decadal scales, and the first evidence from the southern hemisphere for the effects of contemporary ocean warming on gas hydrate stability. Widespread hydrate dissociation results in a highly focused advective methane flux that is not fully accessible to anaerobic oxidation, challenging the assumption that it is mostly consumed by sulfate reduction before reaching the seafloor.

Effect of biogenic fermentation impurities on lactic acid hydrogenation to propylene glycol.

The effect of residual impurities from glucose fermentation to lactic acid (LA) on subsequent ruthenium-catalyzed hydrogenation of LA to propylene glycol (PG) is examined. Whereas refined LA feed exhibits stable conversion to PG over carbon-supported ruthenium catalyst in a trickle bed reactor, partially refined LA from fermentation shows a steep decline in PG production over short (<40 h) reaction times followed by a further slow decay in performance. Addition of model impurities to refined LA has varying effects: organic acids, sugars, or inorganic salts have little effect on conversion; alanine, a model amino acid, results in a strong but reversible decline in conversion via competitive adsorption between alanine and LA on the Ru surface. The sulfur-containing amino acids cysteine and methionine irreversibly poison the catalyst for LA conversion. Addition of 0.1 wt% albumin as a model protein leads to slow decline in rate, consistent with pore plugging or combined pore plugging and poisoning of the Ru surface. This study points to the need for integrated design and operation of biological processes and chemical processes in the biorefinery in order to make efficient conversion schemes viable.

Process model and economic analysis of itaconic acid production from dimethyl succinate and formaldehyde.

A complete process model and economic analysis has been developed for itaconic acid production via catalytic condensation of dimethyl succinate and formaldehyde. The process model is based on experimental yields and selectivities obtained for the condensation reaction and on recovery schemes for itaconic acid developed in our laboratory. For an 18 million kg/yr (40 million lb/yr) itaconic acid production facility with a 10-year lifetime, the model predicts a capital investment of $40 million and an itaconic acid selling price of $2.34/kg ($1.06/lb) to achieve 30% annual return on investment. Feedstock cost is the largest contributor to the price of itaconic acid; succinate conversion and selectivity to the intermediate citraconic acid therefore most strongly influence process economics. Results of these analyses indicate that itaconic acid can be produced catalytically from succinic acid and formaldehyde at lower cost than via the current fungal fermentation route.

Stereoretentive C-H bond activation in the aqueous phase catalytic hydrogenation of amino acids to amino alcohols.

[reaction: see text] At 100 degrees C and 1000 psi of hydrogen, aqueous l-alanine undergoes facile hydrogenation to l-alaninol over a 5% Ru/C catalyst. In the presence of added acid to protonate the carboxylate moiety, the reaction is faster and more selective than analogous reductions of simple alkanoic acids. Stereochemistry at the alpha-carbon is retained despite complete exchange of hydrogen at this site, as shown by deuterium incorporation. Similar stereoretentive C-H bond activation at C2 is seen in l-alaninol itself, and when acid is omitted, in l-alanine. These processes reveal a class of mild, highly stereoretentive C-H bond activations occurring in water over a heterogeneous catalyst.

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 $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 $75 million and a net processing cost of $1.85 per kg SA. Required selling price of diethyl succinate for a 30% annual return on investment is $1.57 per kg.

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

An attractive approach to improving cold flow properties of biodiesel is to transesterify fatty acid methyl esters with higher alcohols such as n-butanol or with branched alcohols such as isopropanol. In this study, the reaction kinetics of Amberlyst-15 catalyzed transesterification of methyl stearate, a model biodiesel compound, with n-butanol have been examined. After identifying conditions to minimize both internal and external mass transfer resistances, the effects of catalyst loading, temperature, and the mole ratio of n-butanol to methyl stearate in the transesterification reaction were investigated. Experimental data were fit to a pseudo-homogeneous, activity-based kinetic model with inclusion of etherification reactions to appropriately characterize the transesterification system.