A Fine, Aged Biomass

You get that big promotion or reach that special milestone and pull out a nicely chilled bottle of ... fermented biomass?

You get that big promotion or reach that special milestone and pull out a nicely chilled bottle of ... fermented biomass?

It doesn’t sound quite right, but bubbly and biofuel may have more in
common than appears at first glance. Sure, one tastes a lot better (that
would be the bubbly), but both are fermented products that start out with
plant matter.

“As a scientist you always try to break everything down to the basics, and
making wine is about fermentation and the product is ethanol. It’s basically a fuel,” says Timo Schuerg, a postdoctoral fellow at the Energy Biosciences Institute who was among about two dozen EBI researchers and
students to get a firsthand look at the winemaking process at a field trip
to Mumm Napa, a well-known producer of sparkling wine in California’s
Napa Valley.

For wine, the biomass in question consists of grapes, specifically varieties of the species Vitis vinifera, which are picked only when certain
sugar levels have been reached – something that's assessed by the Brix measuring system, named for German mathematician and engineer
Adolf Brix.

Once picked, the juice is extracted and fermentation begins. All wines
start out white; red wines get their color from leaving the skins in contact with the fermenting juice. As with current biofuels, it takes yeast
to produce ethyl alcohol, or ethanol. Winemakers may add cultivated
yeasts or let the process take place through naturally occurring ambient yeasts. The yeasts consume the sugar, creating alcohol as a byproduct – but only enough to fuel dreams, not vehicles. Wine alcohol levels
typically run from 12 percent to 15 percent by volume, too low to run
an engine.

Winemakers have an advantage over biofuels producers in that their
feedstock is bursting with easily extracted sugars. And they can sell their
product for $60 a gallon without anyone blinking an eye. Even Two Buck
Chuck, the love-it-or-hate-it famously cheap Charles Shaw wine that sells
for $1.99 in California, works out to about $10 a gallon.

Biofuel developers don’t have that luxury. The essential process of depolymerization – breaking the chemical bonds among the large cellulosic
compounds of a plant’s biomass in order to produce small fermentable
sugars – is still a complex and expensive issue. This means bringing down
the cost of depolymerization is one of the utmost priorities in biofuel research.

In nature, the true experts in depolymerization of plant biomass include
creatures that are defined as filamentous fungi. Schuerg is one of the scientists at the EBI who dedicate themselves to study the filamentous fungus Neurospora crassa, which grows on plant cell wall material and which is primarily found on burnt grasses, sugarcane stalks and sugarcane bagasse.

A primary goal is fostering understanding of how the fungus regulates and uses its enzymes – i.e. specialized molecular tools – to efficiently deconstruct plant cell wall material, something that could eventually lead to easier and cheaper depolymerization.

Fungi are a big part of the wine world, too. Sometimes vintners fight it -
like the mildew that can blight a crop. But yeasts, also fungi, are crucial to
how a wine turns out – enologists can wax quite passionate over the merits of cultivated vs. wild yeasts. The role of yeast in winemaking prompted
some interesting conversations on the EBI field trip, which also included a
visit to the St. Supéry winery. “We had discussions about the yeast strains.
We always came back to our experiences in the lab, actually,” says Schuerg.

Organizers arranged the trip partly to have fun, but also to provide a forum for scientists affiliated with EBI to spend time together since many
are scattered across campus at the University of California, Berkeley.
Mission accomplished on both fronts, says Schuerg. “It’s always good to go
out and see something different. It enriches your mind,” he says.
So which is better – crafting wine or brewing biofuel? Schuerg laughs. “I
would say you need years of experience to make a good wine, and I took
the decision to go for biofuels,” he says. Still, the two worlds could meet
again. If the biofuels team makes a big breakthrough, expect to hear the
sound of champagne corks popping.

 

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