SPOTLIGHT

& Paving the Way for Thermophilic BioethanolProduction

Bioethanol is a promising fuel candidate to replace fossil fuels,especially in the transportation sector. However, only when it isproduced from residual biomass can it actually be considered asustainable biofuel. Pentose sugars, which constitute a largefraction of residual and lignocellulosic biomass, are not fermentedby industrial strains of ethanologenic yeasts. Tomas and coworkershave recently isolated a new extreme thermophilic microorganism,Thermoanaerobacter pentosaceus, which has shown the highestethanol yield from pentose sugars ever reported for a wild-typestrain. In this work, the authors demonstrate that T. pentosaceuscan be used in combination with Saccharomyces cerevisiae toconvert rapeseed straw into bioethanol in a more efficient mannerthan using each microorganism separately. This is an importantachievement because it can be easily implemented into existingbioethanol production plants. Page 1574

DOI: 10.1002/bit.24664

& Predicting Microalgae Growth in PondCultures

Improving the economics of microalgal biofuels productionrequires the identification of novel microalgae strains with superiorbiomass productivities. In order to better achieve this objective, amicroalgae biomass growth model was developed for screeningnovel strains for their potential to exhibit high biomassproductivities in outdoor ponds. Growth is modeled by firstestimating the light attenuation by biomass according to Beer–Lambert’s law, and then calculating the specific growth rate indiscretized culture volume slices that receive declining lightintensities due to attenuation. The model uses only two physicaland two species-specific biological input parameters: incident lightintensity, culture depth, as well as the biomass light absorptioncoefficient and the specific growth rate as a function of lightintensity. The model was successfully validated using LED-lightedraceway pond cultures operated at constant light and temperature.Future work involves using the model to predict microalgaebiomass growth in outdoor ponds. Page 1583

DOI: 10.1002/bit.24665

& Novel Pathways Toward 5-CarbonBioplastics Building Blocks

Polyamides, which are composed of amino acid homopolymers orcopolymers of diamines and diacids, are promising and diversetargets within the renewable bioplastics spectrum. Today, suchmonomers are principally derived from petroleum resources. Inrecent years, however, the microbial production of 4- through6-carbon monomers such as succinic acid, adipic acid, putrescine,and cadaverine have been reported. In the present work, Adkins,Jordan, and Nielsen describe how, through de novo pathwayengineering, the ‘bottom up’ microbial biocatalysts can beengineered to produce the 5-carbon polyamide building blocks5-aminovaleric acid and glutaric acid; precursors to nylon-5 andcopolymers such as nylon-5,5, for example. To do so, the lysinedegradation pathway native to Pseudomonas sp. was systematicallyreconstructed and tuned in a strain of Escherichia coli engineeredfor lysine over-production. Initial strains achieved 5-aminovalericacid and glutaric acid titers as high as 820mg/L. This work couldhelp to further expand the diversity of bioplastics that can beproduced from renewable resources. Page 1726

DOI: 10.1002/bit.24666

& Introducing Cell Communication

Challenges for generating efficacious anticancer therapies remainand the need for alternative approaches beckon. Bacteria representgreat potential as vectors for therapeutic intervention since they areknown to colonize tumors and can be engineered to produceproteins. The current offering from the Forbes group marshalsseveral forces to assemble a powerful cell-communication systemthat builds on Salmonella’s innate ability to distribute actively totumor tissue over normal tissue. The quorum sensing apparatusfrom Vibrio fischeri was integrated into Salmonella such that thecell-communication gene circuit was connected to a fluorescentreporter gene, allowing the authors to track outcomes. Attributessuch as increased protein expression, increased sensitivity to thechemical trigger, regulation and control of the chemical trigger,persistent gene expression after removal of the initial trigger, andpenetration into tumor tissue could all be assessed relative to non-communicating controls. Their design for cell communicationmight allowmultiple applications not only for cancer therapy usingother extracellular inducible systems but also in broader biologicalengineering applications such as bioremediation. Page 1769

DOI: 10.1002/bit.24667

Published online in Wiley Online Library

(wileyonlinelibrary.com).

� 2013 Wiley Periodicals, Inc. Biotechnology and Bioengineering, Vol. 110, No. 6, June, 2013