代谢工程学可使海藻作为生物柴油的原料

Is red seaweed（海藻） a viable¹ future biofuel? Now that a University of Illinois metabolic²（新陈代谢的） engineer has developed a strain of yeast³（酵母） that can make short work of fermenting⁵（发酵） galactose（半乳糖） , the answer is an unequivocal（明确的，不含糊的） yes. "When Americans think about biofuel crops, they think of corn, miscanthus（芒草） , and switchgrass（柳枝稷） . ln small island or peninsular nations, though, the natural, obvious choice is marine⁶ biomass," said Yong-Su Jin, a U of I assistant professor of microbial genomics and a faculty⁷ member in its Institute for Genomic Biology.

Producers of biofuels made from terrestrial（地球的，陆地的） biomass crops have had difficulty breaking down recalcitrant⁸ fibers⁹ and extracting fermentable¹⁰ sugars. The harsh pretreatment processes used to release the sugars also resulted in toxic¹¹ byproducts, inhibiting¹² subsequent microbial fermentation, he said.

But marine biomass can be easily degraded to fermentable sugars, and production rates and range of distribution are higher than terrestrial biomass, he said.

"However, making biofuels from red seaweed has been problematic because the process yields both glucose¹³（葡萄糖） and galactose, and until now galactose fermentation has been very inefficient," he said.

But Jin and his colleagues have recently identified three genes¹⁴ in Saccharomyces cerevisiae（酿酒酵母） , the microbe most often used to ferment⁴ the sugars, whose overexpression increased galactose fermentation by 250 percent when compared to a control strain.

"This discovery greatly improves the economic viability¹⁶ of marine biofuels," he said.

Overexpression of one gene¹⁵ in particular, a truncated¹⁷（缩短了的） form of the TUP1 gene, sent galactose fermentation numbers soaring. The new strain consumed both sugars (glucose and galactose) almost three times faster than the control strain—8 versus¹⁸ 24 hours, he said.

"When we targeted this protein, the metabolic enzymes¹⁹ in galactose became very active. We can see that this gene is part of a regulating or controlling system," he said.

According to Jin, galactose is one of the most abundant sugars in marine biomass so its enhanced fermentation（发酵） will be industrially useful for seaweed biofuel producers.

Marine biomass is an attractive renewable source for the production of biofuels for three reasons:
production yields of marine plant biomass per unit area are much higher than those of terrestrial biomass
marine biomass can be depolymerized（解举） relatively²⁰ easily compared to other biomass crops because it does not contain recalcitrant lignin（木质素） and cellulose crystalline structures
the rate of carbon dioxide fixation by marine biomass is much higher than by terrestrial biomass, making it an appealing option for sequestration（隔离，扣押） and recycling of carbon dioxide, he said.