Inhibitions from oligomers

An intersting research paper with new findings: "xylobiose and higher xylooligomers were shown to inhibit enzymatic hydrolysis of pure glucan, pure xylan, and pretreated corn stover."

"Thus, b-xylosidase alone does not appear to be sufficient to hydrolyze high DP soluble xylooligomers, and supplementation with both xylanase and b-xylosidase appears desirable to realize high monomeric xylose yields, as found for pure xylan and AFEX and SO2 pretreated corn stover."

What about other oligomers such as mannooligomers in softwood?

Pretreatment: Low temperature and atmospheric

Here is a paper on low temperature pretreatment. What other methods?

• Alkaline peroxide?
• Oxygen-alkaline treatment?
• Ozone?
• Liquid ammonium?

All of these work but which one is more practical in terms of environmental issue and cost?

What about biopulping process?

Two new papers on genetic modification of biofuel feedstocks

1. Genetic modification of lignin biosynthesis for improved biofuel production

2. Genetic improvement of C4 grasses as cellulosic biofuel feedstocks

Plant genetic engineering for biofuel production- a problem solver from the root

"Genetically engineering plants to produce cellulases and hemicellulases, and to reduce the need for pretreatment processes through lignin modification, are promising paths to solving this problem, together with other strategies, such as increasing plant polysaccharide content and overall biomass." A review paper published in Nature summarized the research progress in these aspects.

Cheap sugar: How can it be cheaper?

It is known that feedstock cost account for significant part of overall ethanol production cost. The key is to obtain cheap fermentable monomer sugars from lignocellulosic biomass with the following factors:
· Monomer sugar recovery yield. If we look at biomass, only ~65-70% of cell wall is carbohydrate that is our target to convert into monomer sugars. The question is how to efficiently hydrolyze it with high yield. Chemically or enzymatically? Currently both cannot achieve high sugar yield and high efficiency. The combination of chemical and enzymatical hydrolysis is the direction. However, more factors need to be considered to achieve high sugar yield when talking about a commercialized technology:
o Recoverable/recyclable chemicals that minimize the chemical cost and waste treatment
o The pH of pretreatment that impacts reactor metallurgy
o The temperature of pretreatment that impacts energy usage
o The robust of enzymes that reduce the loading and increase the efficiency