Section Four
BIOLOGICAL SYSTEMS-A. GENERAL
28    THE EFFECTS OF FREEZE-DRYING AND STORAGE ON A
PHENOL DEGRADING BACTERIAL SUPPLEMENT
Roberta L. Gaiek, Engineer
Malcolm Pirnie, Inc.
Buffalo, New York 14219
Clifford R. Lange, Graduate Student
A. Scott Weber, Associate Professor
Department of Civil Engineering
State University of New York at Buffalo
Buffalo, New York 14260
INTRODUCTION
Commercial bacterial supplements have been promoted as an effective and economical way to
enhance biological treatment processes. Addition of these specialized bacteria to the naturally occurring population of a bioreactor for enhancement of population diversity and/or activity is known as
bioaugmentation. Bioaugmentation can be effective in increasing biodegradation by 1) adding bacteria with enzymatic systems capable of biodegrading previously persistent organics, and/or 2) adding
bacteria with higher metabolic rates. In particular, bacterial supplements are often promoted as being
capable of rapidly initiating biodegradation of many xenobiotic compounds including aromatics (such
as phenol and chlorinated phenols). However, past studies have shown that lengthy acclimation
periods may be required from these specialized bacteria prior to target compound
biodegradation1-2'3.
Typically, commercial supplements are freeze-dried to allow for ease of storage and application.
Unfortunately, this preparation procedure often results in viability losses and reductions of metabolic
activity upon supplement reconstitution which may lead to poor supplement performance. The purpose of this paper is to present and discuss the results of a laboratory investigation conducted to
investigate the effects of freeze-drying and storage on bacterial supplement performance.
BACKGROUND
Factors identified as important for the successful employment of commercial bacterial supplements
are discussed in this section. Lange2 has outlined these parameters as including: supplement viability,
presence and retention of necessary genetic coding, and activation of inducible enzyme systems
(acclimation). The effect of these factors on supplement biodegradation potential is discussed below.
Supplemental Viability
To achieve enhanced biodegradation through supplementation, the biological treatment system
must first be inoculated with the desired organisms. Subsequently, the bacterial supplement and/or
their genetic coding for target compound biodegradation must be retained in the system. Therefore,
supplement viability plays an important role in bacterial supplement performance. If supplement
viability is lost at any time during the bioaugmentation process, no enhancement of biodegradation
will occur.
There are two major factors which can influence the presence of viable supplement bacteria in the
biological system. The first factor is the number of viable organisms delivered into the process being
augmented. This initial viability of supplement bacteria is influenced by a number of factors including
the freeze-drying and storage process. The second key factor influencing the number of viable supple-
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