Helping Ethanol Producers Operate in the ‘Sweet Spot’

Novozymes describes the process behind finding innovative solutions
By Guillermo Coward-Kelly | July 21, 2011

Part of being successful in business—or virtually any endeavor—is knowing when to keep to conventional wisdom and when to go out on the proverbial limb and challenge “the way we’ve always done it.” It is indisputable that the ethanol industry could have never moved from its infancy to where it is today without a healthy dose of unconventional thinking and ingenuity. At Novozymes, a major component of our “Rethink Tomorrow” strategy involves moving the industry forward with innovative products and services, as well as testing new ideas and sharing what we’ve learned.

Such has been the case with a new analytical method developed by Novozymes scientists that can change the way ethanol producers monitor their processes to optimize performance.  Born in the lab, nurtured in a week-long creative exercise, and brought to fruition by initiative and determination, this new take on a long-standing concept is already driving process improvements at ethanol plants.

One of the most commonly used indicators of fermentation performance in an ethanol plant is the measurement of the DP4+ peak. Abnormal concentrations are often presumed to mean potential yield loss. New information on DP4+ and residual starch is available to assist plants with measuring process efficiency and data-based decision making. 

Previous studies have shown that the DP4+ peak contains ions, proteins, dextrins and other soluble compounds from corn, yeast, enzymes, salts and acids that come from the fermentation or are added during sample handling.  The peak composition is complex and ever-changing. Plants that use the DP4+ peak as an indicator of incomplete hydrolysis and fermentation need to understand that a sudden change in DP4+ peak concentration may not be indicative of incomplete hydrolysis and fermentation, but can actually be a result of changes in backset, feedstock handling or other processes. Misinterpretation of these readings may lead to a cascade of decisions that can significantly impact plant operations.

Based on these findings, a new pretreatment method has been developed that combines a simple and robust preparative chromatography step with the high-performance liquid chromatography (HPLC) method commonly used by the ethanol industry to analyze total residual sugars, fermentation health, yeast stress and ethanol concentration.  All of these measures are needed to calculate ethanol yield, and HPLC was adopted as the industry standard long ago.

This pretreatment method is based on ion exchange—a well-known technique that has been used in the starch and brewing industries for many years to clean up wet mill streams. In its new application for the ethanol industry, this preparative step removes ion contaminants from the fermentation drop sample that contribute to, and possibly distort, the DP4+ peak. The resulting DP4+ measurement more accurately represents the amount of residual sugars remaining in the sample. This information enables ethanol producers to make better decisions as they work to investigate abnormal DP4+ readings and maximize yield. 

In our testing, HPLC data obtained after this ion exchange process typically shows a reduction in the size of the DP4+ peak, suggesting that the contribution of fermentable dextrins to the total residual sugars measurement is significantly less than might be expected. In a standard sample study, our scientists found that the DP4+ peak at fermentation drop was composed of 70 percent ions, 20 percent proteins and other solubles, and only 10 percent dextrins.

Innovation to Real-World Application

Novozymes scientists are always encouraged to think outside the box, but that’s not always easy to do when dealing with the workload of a typical day. That’s why Champagne Week is so important. This yearly event, when Customer Solutions and R&D staff are allowed to venture away from their standard duties to work on a new idea that they haven’t had time to explore, is a unique way to promote creativity. It was during one of these events that the concept of applying ion exchange to HPLC analysis was finally able to be investigated.

The idea was the brainchild of Billy Whitlock, a scientist at the Novozymes Midwest Customer Solutions Center in Ames, Iowa. Whitlock, along with colleague Susan Johnson, a senior research associate based in Franklinton, N.C., took advantage of their time during Champagne Week to delve into the possibilities that this new troubleshooting tool might hold.

According to Whitlock, “The fact that the HPLC’s DP4+ peak was a catchall for soluble components present in fermentation was already well-known. We saw this technology as an opportunity to remove a major chunk of that “catch all” and get closer to what customers really want to measure—how much sugar am I leaving behind? As it turns out, there’s usually more salt (ions) than sugar left over in well-run industrial fermentations.”

At the end of Champagne Week, senior scientist Rogerio Prata was asked to evaluate Whitlock and Johnson’s work and come up with a customer-friendly approach for implementation. It was Prata who took the original idea to the next level and developed the new application tool for an old solid phase extraction technique—a special cartridge to process the sample through. “Once management made the decision to revisit this topic, we employed a variety of laboratory techniques to evaluate methodologies and ensure the integrity of the results,” Prata explains. “Our overall goal was to develop a simple, user-friendly method to give our customers a better estimation of the contribution of dextrins to the DP4+ peak.“

Preliminary results in real-world ethanol plants have been very encouraging. One of our customers used the pretreatment method at multiple plant locations and consistently measured lower readings of real soluble substrate. The data has continued to show that only about one-third of the DP4+ value at fermentation drop is actual remaining soluble substrate. The benefit to the plants has been immediately helpful. Their ability to monitor residual sugars at multiple locations has resulted in improved standardization and consistency, and serves as a helpful benchmarking tool.

Management Benefits

Learning more about the composition of a plant’s normal DP4+ peak makes it easier to investigate reasons for abnormal variations in DP4+ concentrations. This insight leads to improved decision making by the plant management team and assists in their efforts to maximize ethanol yield. Further, this knowledge tells ethanol producers where they should focus their attention. For example, do they need to add more glucoamylase to their sample? When should they add enzymes?

This pretreatment tool has many beneficial applications for ethanol producers. As results of each assay answer relevant questions about their process operation, they are able to effectively troubleshoot ways to achieve maximum feedstock conversion and ethanol yield. A better understanding of the DP4+ peak serves to eliminate a lot of guesswork about factors such as dosing strategy.

We are still in the early stages of incorporating this tool with our customers, but we are excited about its potential to bring knowledge and innovation to the ethanol industry. We know that when our industry wins, everyone benefits. Knowledge is power and this new analytical method will enable our customers to better understand and manage their ethanol production.

Author: Guillermo Coward-Kelly
Staff Scientist/Team Leader
Novozymes Biofuels R&D