Sunday, April 15, 2012

Degree of biomass substrate solubilization

When evaluating the effect of pretreatment and especially enzymatic hydrolysis of biomass, we normally measure the monomeric sugar produced. At most time, quite a lot of soluble oligomers existing in the hydrolyzates that could not be measured by the standard HPLC analysis, which will lead to lower hydrolysis yield. This can be confirmed by post-dilute acid hydrolysis, showing several fold increase in  monomeric sugars (glucose and xylose) yield. The reason for this is that most of the commercial enzyme cocktails are not for global use and need customization for a specific biomass substrate. Some new technology ends up with strains than can work on low DP soluble sugars. Therefore, measurement of the degree of biomass solubilization after pretreatment or/and enzymatic hydrolysis will be useful information for the estimation of the treatments.  A weight loss is rough, but quick method.

Tuesday, November 8, 2011

Moderate pretreatment: a practical approach for bioconversion of cellulosic biomass

When pretreating biomass under harsh conditions (extreme pHs and high temperatures), biomass chemical components will degrade into by-products that become inhibitors for the subsequent processing. However, moderate pretreatment can be developed to avoid sugar degradation and toxic compounds formation during pretreatment. As a result, a whole slurry process without inter-stage washing/detoxification can be used, which can significantly reduce capital/operational cost. A moderate pretreatment must remove some lignin but do not break down lignin to simple compounds.It should achieve some defibrillization without much sugar degradation. In a word, It is enough as long as cell wall pores/channels are opened. "Over pretreatment" may improve cellulose accessibility but inevitably cause other chemical components degradation. The right degree of pretreatment is the key. 

Thursday, November 3, 2011

The solution to 7 Billion Consuming Resources

On 11/01/2011, the world population hit 7 billion, a warning to the world’s resources: limited food, absolute water scarcity, increasing consumption of non-renewable oil.

One solution: technological advancements and a free market.

  • Desalination: to get fresh water from the sea!
  • Hybrid and high yield food: Transgenic plants?
  • Alternative energy- biofuels,natural power sources like solar and wind may be an alliterative before our fossil fuels run out.

Wednesday, November 2, 2011

Biomass particle size

It is agreed that biomass feedstock particle sizing can impact the economics of cellulosic ethanol commercialization through its effects on conversion yield and energy cost. Physical size reduction can not always achieve expected effect of biomass enzyme digestibility. For example, the thickness of woody biomass play more critical role in chemical pretreatment of wood chips than its length. Defibrillation of grass biomass is more efficient than size reduction in terms of enzymatic hydrolysis.

Therefore, for practical application, an appropriate size reduction needs to be selected based on the biomass type,what chemicals to be used for pretreatment. The smaller does not mean the best!

Monday, October 31, 2011

Xylooligomers are strong inhibitors of cellulose hydrolysis by enzymes

It has been known that xylooligomers are  the inhibitors to enzymatic hydrolysis. An customized enzyme cocktails have to be developed and applied on specific biomass substrates. Here are two recently published papers reported their research results on this issue.