"The cost barrier standing in the path of economical and scalable biofuels and chemicals production can be broken," Proterro CEO Kef Kasdin said here at the Advanced Biofuels Leadership Conference.

Updating attendees on Proterro's progress in developing an economical non-crop-based, noncellulosic, fermentation-ready, clean sugar feedstock, Kasdin reported that Proterro "has successfully and consistently demonstrated high sucrose productivity in its own laboratory, as well as in the field, at two independent greenhouse sites."

At the three locations, two in the Midwest and one in Northern California, "Our modular photobioreactors yielded consistently high sucrose production, in two cases for more than three months of continuous operation," she said.

"We saw no contamination affect the sucrose productivity, and even when we deliberately introduced microbial contamination into the photobioreactors the cyanobacteria coexisted with these other organisms and sucrose productivity did not diminish," Kasdin continued.

The results of the field trials confirmed that Proterro can develop sucrose at a cost, inclusive of capital costs, that is already competitive with today's cost of alternative sources of sugar, including sugar cane, corn and cellulosic sugars, Kasdin noted.

"We continue on a promising path to a less-than-10-cent-per-pound sucrose."

Kasdin explained that Proterro has taken cyanobacteria that naturally produce sucrose-and only sucrose- and successfully genetically engineered them so that they secrete the sucrose in a continuous, high-yield process.

"We grow these cyanobacteria, which only need sunlight, carbon dioxide, nutrients and water, in a very different way from typical algae cultivation approaches," she said.

"Most algae cultivation systems employ classical liquid phase bioreactors in a wide variety of designs, but Proterro has demonstrated and scaled an alternative approach - a solid-phase modular photobioreactor that optimizes the organisms' access to light and carbon dioxide, and uses significantly less water," Kasdin said.

"The organisms grow on a composite fabric substrate, enclosed in a photobioreactor that surrounds them with their carbon-dioxide feedstock. Water and nutrients are trickled into the photobioreactor, with its modular nature affording a robust, scalable and controlled cultivation environment for photosynthetic organisms.

"The agricultural biomass used today to produce biofuels and chemicals requires time to grow and expensive harvesting, storage and extraction steps to produce a clean fermentation-ready sugar," Kasdin noted.

"Our patent-pending process produces ready-to-ferment sucrose without any of those steps and currently yields 10 times more sucrose per acre than sugarcane - with more improvements still to come."

Proterro, which has developed a robust economic model, plans to go to market through joint ventures with select partners who can use Proterro's sucrose to produce, through existing industrial methods, downstream products, including commercial scale fuels and chemicals, Kasdin said.

The company will position its photobioreactors at the front end of these downstream facilities, where the carbon dioxide generated during fermentation could be captured and used to make even more sugar.