Dr. Dennis Bayrock

Global Director Fermentation Research Lactrol (Phibro epg)

Session: Speaker – Fermentation Panel

Topic:Improper CIP management and persistent bacterial contaminations


Fuel ethanol plants utilize cleaning in place (CIP) procedures to prevent bacterial contamination. Nearly every unit operation at a fuel ethanol plant utilizes CIP and each has its own respective CIP procedure. Typically, plants depend on using 2.5-5% w/v caustic solutions and using the 4 T guidelines for CIP: Time, Temperature, Titre, and Turbidity to properly CIP multiple locations within the plant.

Other than the bacteria that enter the plant via corn, water, and other inputs, improper or lack of CIP at a fuel ethanol plant remains the leading cause for recurring and persistent bacterial contaminations within the plant. Complicating this picture are the potential organic precipitates formed by chemical and biological reactions during CIP. Precipitates form an excellent scaffold for bacteria to colonize due to the increased surface area – that can increase by over 400% depending as precipitate particle size decreases. The severity of bacterial contamination at ethanol plants is reduced where precipitates have either been removed (i.e. via shutdown) or formation has been prevented (i.e. pocess changes and/or products).
Among the precipitates that can form at the ethanol plant during CIP are carbonates – insoluble hard crystals formed from the reaction of CO2 and caustic. In distillation, carbonates can be dissolved and removed with the addition of acids, but acid addition is not an option in the spent caustic tank as the caustic solution here is needed to provide multiple CIP operations at the plant. The strength of this caustic solution can be refortified with fresh caustic, but any carbonates within the tank are not usually removed until the plant decides to purge the spent caustic tank. Worse, formation of carbonates neutralizes the strength of caustic solutions. The reuse of caustic with carbonates may thus negate the Titre strength of the caustic solution, provide increased colonization power of bacteria when crystals are deposited (and neutralized) in pipes and vessels, and decrease the overall effectiveness of CIP within the plant.

This seminar will focus on the chemistry and formation of carbonates within the CIP system of a fuel ethanol plant. The discussio

n will highlight the traditional titration method of determining caustic strength (which may be overestimating true caustic strength) and suggest alternative proven methods which account for carbonate presence. Diagrams and pictures will be presented which indicate the potential severity of recycled caustic containing carbonates. Lastly, multiple recommendations made to ethanol plants will be discussed that help increase the rigour of CIP at the plant, and help minimize the effect of bacterial contaminations.


Dr. Dennis Bayrock completed his PhD from the University of Saskatchewan. He specializes in multistage continuous fermentations and in microbial contamination in fuel alcohol fermentations. In total, Dr. Bayrock’s career in practical research and international experience has spanned over 26 years in the fuel ethanol industry.

Dr. Bayrock is an Adjunct Professor at the University of Minnesota where he conducts research and provides teaching in fuel ethanol fermentations. In addition to his faculty position, Dennis continues his responsibilities in research and development for Phibro at PhibroChem’s Ethanol Performance group lab in St. Paul, MN.

During his career he has visited numerous fuel and potable alcohol plants in Canada, US, Jamaica, Puerto Rico, Brazil, and Thailand and carried out plant microbiological audits, optimized addition of antibiotics on a plant-by-plant basis, and optimized plant fermentation conditions. Dr. Bayrock has demonstrated his expertise in identifying, cataloging, and screening various microbial contaminants from the fuel and potable alcohol industries. He has made numerous emergency “house calls” to plants suffering from contamination and has successfully diagnosed, treated, and restored plants to normal operation. As an internationally invited lecturer, Dr. Bayrock has been well received at conferences in the fuel and potable alcohol industries, and has presented numerous seminars on general plant operations and on multiple topics relating to yeast and bacteria.