Guenter Pollach's microbiological abstracts

Abstracts of Microbiological Papers

Pollach, G.: Introduction of antimicrobials from plants to the sugar industry.
Presented to the workshop "Anti-microbials from plants: Opportunities and barriers", organized on 27^th-28^th January 2005 at York St. John College by the National Non-Food Crops Centre (NNFCC), York, G.B.

Abstract: After an introduction to white sugar, sugar technology, beet extraction and thermophilic micro-organisms, three natural antibacterials stemming from the hop plant, the pine tree and from palm kernels are presented. These natural substances can be used in sugar factories instead of formaldehyde, which was recently classified as carcinogenic. Under thermophilic conditions Gram-positive micro-organisms are selected, which are sensitive to the natural antibacterials. However, even these micro-organisms may become insensitive to natural products after repeated application. In comparison to human health and the use of antibiotics, it is necessary to have different natural antibacterials, in order to meet most of the constraints, caused by micro-organisms in sugar factories.

Pollach, G.; Hein, W.; Beddie, D.: The concept of different natural anti-bacterials for the sugar industry (SPRI conference 2004, Atlanta).
Zuckerindustrie 129 (2004) pp. 555-564.

Abstract: Palm kernel fatty acids and especially the most effective myristic acid are presented for the sugar industry, which could be used as natural antibacterial aids to displace adapted strains. After a survey of existing literature, results of laboratory trials were carried out to demonstrate the mechanism of action, as well as influences of chain length, temperature, pH value, etc. Further, results from full-scale factory trials during the beet campaigns 2002 and 2003 are presented. During 2002, a rosin-insensitive strain occurred in a beet extraction tower and could be eliminated by shock dosing of myristic acid. This result already stresses the importance of natural alternatives for elimination of adapted strains, to keep the level of fermentation low in every case. In 2003 satisfactory effects were achieved with myristic acid in two other Agrana factories. The new product is precipitable with calcium and mainly removed from the process stream via pulp, lime sludge and molasses.

Pollach, G.; Hein, W.; Beddie, D.: Application of hop beta acids and rosin acids in the sugar industry (SPRI conference 2002, New Orleans).
Zuckerindustrie 127 (2002) pp. 921-930.

Abstract: In 1994, hop products were successfully used for the first time to combat bacteria in beet extraction. This was a totally new field for the use of hop products, compared with their traditional use in breweries. Today an alkaline solution of hop beta-acids is used in sugar factories under the trademark BetaStab^®. Hop beta-acids have turned out to be very effective against formation of NO₂ and anaerobic infections in tower extractors, which are often operated intentionally with lactic acid fermentation. Hop beta-acids have additionally proved effective in the field of thick juice storage. Sometimes, in the case of lactic acid control, a selection of less sensitive organisms is observed and a second disinfectant has to be used, alternating with hops. Thus an idea was born to use rosin acids as a further harmless natural biocide. Results from laboratory trials, full scale trials and some first studies on residues are presented. Rosin acids show a potential to be used in the sugar industry, either alternating with hop products or to create products which are more cost effective.

Hollaus, F.; Hein, W.; Pollach, G.; Scheberl, A.; Messner, P.: Nitrite formation in the thin juice by Thermus species (German). Zuckerindustrie 122 (1997) pp. 365-369.

Abstract: High concentrations of nitrite in molasses of an Austrian sugar factory gave a rise to a systematic survey in order to identify location and cause of the formation of nitrite. The high levels could only partially be explained by microbial reduction of nitrate in the diffusion plant. It turned out that the critical rise of nitrite occurred during the passage of thin juice through a newly installed softening plant. Careful inspection of the plant revealed massive bacterial films on the gravel bed of the ion exchange columns, although the temperature of the thin juice in the exchange columns had been kept at 80°C, thus exceeding the temperature tolerance limit of thermophilic, sporulating bacteria. However, cultivation of the mixed population of isolated bacteria in the laboratory confirmed their ability to reduce nitrate at 80°C. Upon growth in single cell colonies and both physiological and microscopical examination their affiliation to the genus Thermus was shown, which represents an extremely thermophilic, non-sporulating group of Gram-negative bacteria. These results mean that in sugar factories bacterial activity has to be taken into account also in such sectors which hitherto have been regarded as non-critical.

Pollach, G.; Hein, W.; Leitner, A.; Zöllner, P.: Detection and control of strictly anaerobic, spore-forming bacteria in sugarbeet tower extractors. Zuckerindustrie 127 (2002) pp. 530-537.

Abstract: Clostridial fermentation during extraction contributes to an elevated content of volatile fatty acids in the process stream of a sugar factory and thus to impairment of molasses quality. Furthermore, unpleasant odor and elevated TOC emissions are bad side-effects. Hop products, introduced to the sugar industry by Zuckerforschung Tulln (ZFT), seem to be useful in controlling such misfermentation. A dosage can be triggered by a signal from an on-line hydrogen detector, when Clostridia appear. With periodic application of hop products, a parallelism between the appearance of butyric acid and an unknown, UV absorbing substance was observed, which was identified as uracil. Uracil has not yet been described in the context of microbiology of sugar production, but in contrast to volatile fatty acids, no inhibition of yeast growth has been observed. However, due to its characteristic UV absorption at 258 nm, it can serve as an HPLC-indicator to detect Clostridial fermentation in tower extractors.

Pollach, G.; Hein, W.; Rösner, G.: New findings towards solving microbial problems in sugar factories. Zuckerindustrie 124 (1999) pp. 622-637.

Abstract: This paper contributes to the existing body of knowledge on microbiology of beet extraction and thick juice storage, including new measures against micro-organisms. A striking parallelism between nitrite limitation and and acetic acid limitation in full-scale trials in which hop acids were used led to laboratory trials, which showed that acetic acid was formed during nitrite formation. Further trials, which are important for pulp ensiling, showed a switch-over from an unwanted butyric acid formation to lactic acid formation on continuous beta-acid dosage to press water. The authors point to successful trials abroad with full suppression of micro-organisms, because rather high bacterial levels are necessary to run Austrian factories. During the last campaign, the suppression of micro-organisms was improved by new hop products based on alkaline solutions. New investigations on the fate of beta-acids showed a low carry-over of 25% of beta-acids from extraction towers to the raw juice. With improved sensitive methods, white sugar samples showed low values of 0.02 mg/kg of beta-acids.
As to thick juice storage, hop products were not successful as a surface treatment. Thus, treatment with caustic soda solution is recommended instead of a possible formalin application. Independent of the surface, the first positive results were obtained with hop-acid applications to the bulk of the thick juice as a means of controlling bacterial activity there.

Hein, W.; Pollach, G.: New findings with the use of hop products in the sugar industry (German). Zuckerindustrie 122 (1997) pp. 940-949.

Abstract: During the 1996 beet campaign hop-base extract was again used in several factories in full plant scale to reduce bacterial activity in sugar beet extraction. By dosing hop-base extract periodically at mid tower position in amounts of 10 g per ton of beet, the lactic acid content of raw juice was reduced to 400 mg/kg raw juice, without severe influence on the fermentation in the upper part of the tower. The dry substance of pressed pulp was increased to 30% by a residual fermentation. Rapid dosing with high actual concentration, as well known from formalin, is also advantageous for hop extract. Existing devices in Austrian factories must be improved accordingly in the future.
In an aerobic trough diffuser with rather low presswater temperatures it was necessary to use 25 g hop-base extract per ton of beet to achieve a similar residual lactic acid concentration. Under these temperature conditions only formalin was able to inhibit bacterial activity completely. In contrast to the reduction of lactic acid, especially nitrite formation could be avoided, and acetic acid formation which is typical of aerobic extraction equipment was largely reduced. In case of acetic acid and nitrite, base axtract was more effective than a combination of a dithiocarbamate product, a iodophore product and chlorite of lime.
Investigations on the fate of hop extracts showed that values in the products sugar, molasses and pulp are undetectable or uncritical, even under shock-dosing conditions.

Pollach, G.; Hein, W.; Hollaus, F.: Use of hop products as bacteriostaticum in the sugar industry (German). Zuckerindustrie 121 (1996) pp. 919-926.

Abstract: Research has been carried out to determine whether formalin, a widespread processing aid in the sugar industry, could be replaced by hop products principially. It was found that a product called "Base-extract" exists in the hop industry, whose price, based on effect, is able to compete with formalin. The activity of this extract is based on a high content of bacteriostatically efficient hop-beta-acids. During experimental stage dosing of this pasty and water-insoluble product was a problem, which was overcome by emulsifying with sorbitol ester or in case of short pipes by direct dosing of warmed extract. Under Austrian conditions, i.e. with an acceptance of microbial acid formation in the upper part of the extraction towers to improve pulp pressing, the content of lactic acid in the raw juice could be reduced to approx. 400 mg/L by dosing of Base-extract. After juice purification nitrite-forming micro-organisms, within a juice softening equipment by an ion exchanger were successfully controlled with the help of Base-extract. It was found that also in this case hop constituents were inactivated to the extent that no harmful enrichment in molasses occured.

Hein, W.; Pollach, G.; Rösner, G.: Studies on Microbial Activities during Thick Juice Storage. Zuckerindustrie 127 (2002) pp. 243-257.

Abstract: The paper deals with investigations and measures relating to microbial activities on the thick juice surface, as well as activities in the main bulk during storage. Whilst in the first case yearlong experiences on a technical scale exist, in the second case, results from laboratory and pilot-trials are available.
In recent years it has been possible to store thick juice at the Tulln sugar factory, without the addition of formaldehyde, from January to September. During this time, the surface was protected by layering with NaOH. This was originally carried out by means of chains and floating devices and was was subsequently changed to nozzle spraying. Additional improvements during interim storage, such as pasteurization of the thick juice cooler and surface protection by spraying with NaOH has provided optimum storage conditions in 1999 and 2000. To detect surface microbial activity ethanol determination in the headspace was tested. This was possible via an NIR-probe, provided the activity had reached a certain level.
In a 500 m3 tank, partial success in inhibiting surface activity was achieved by spraying with a mixture of potassium sorbate and hop-beta-acids. Earlier observations from laboratory trilas, that the addition of hop-beta-acids slows down microbiological activities, could be confirmed in pilot scale trials. Addition of 3 mg/kg hop-beta-acids to thick juice at 60 % DS considerably extended the time without invert sugar and acid formation, when compared to a blank. As a consequence of the addition of hop-beta-acids during thick juice storage, their fate in crystallisation was investigated. Trials on a factory scale showed that hop-beta-acids, added in different, sometimes excessive amounts, were recovered almost proportionally with the normal ash components on the surface as well as within the sugar crystals. An addition of 3 mg/kg of hop-beta-acids yielded values of less than 0.1 mg/kg of sugar.
Micro-organisms causing a pH value drop in stored thick juice could be propagated semi-continuously in the laboratory. These are cocci, occurring partilly in clusters, which are able to degrade monosaccarides to lactic acid. As an immediate measure to counteract a pH value drop in the whole storage tank, spraying with NaOH solution having a higher density than thick juice (33 %) was tested.

Hollaus, F.; Pollach, G.: Studies of thermophilic breakdown of sucrose, glucose and fructose during beet extraction. Zuckerindustrie 118 (1993) pp. 169-179.

Abstract: Since the 1991 campaign, the use of formalin in Austrian sugar factories has been completely abandoned. This originates on the one hand from a management-order and on the other hand from the effort to improve pulp pressing with the aid of microbiological acid formation in the extraction process. The advantage of well-pressed pulp is greatest if the acid is formed from glucose and fructose and not from sucrose. In this case the fermentation is merely taking the place of the conversion of the monosaccharides to acid in the juice purification. The results of monosaccharide balances determined in extraction plants show bacterial activity variants, ranging from sucrose breakdown almost exclusively to principally invert sugar breakdown. Comparable fermentation patterns have been found in laboratory tests and with pure isolated bacteria cultures. Extrection temperatures above 70°C have been found to favour the decomposition of monosaccharides by thermophilic bacilli.

Pollach, G.; Hollaus, F.: Use of monosaccharide degrading infections in diffusion to improve pulp pressing (German). Zuckerindustrie 113 (1988) pp. 132-136.

Abstract: Decomposition of monosaccharides has been observed during studies of the efficiency of desired infections in the extraction plant of a sugar factory during the 1985 campaign. Within the framework of the present paper an attempt was to be undertaken during the campaign 1986 to determine whether these findings could be confirmed and what would be the results of a cost-utility study within this context. For this purpose, several assessments of the pressability of beet pulp and sugar losses were made under conditions of an uncontrolled infection. A further study was intended to determine, whether the continuous addition of formalin in the lower regions of the extraction towers could limit the infection without any interference with pressability. Finally an attempt was made to achieve a comparison between infected and sterile operation of the extraction facility with the aid of shock dosage.
While with experiments during the first 15 days of campaign better results were achieved by means of the uncontrolled infection than with formalin dosing, in respect of strong influence on the pressed pulp dry substance, experiments later in the campaign showed that limitation of the infection by continuous dosing with formalin gave more favourable results. In a comparison between shock dosage and uncontrolled infection, the latter gave better results as in the 1985 experiments, owing to the decomposition of glucose and fructose and the improvement in the pressability of the exhausted pulp - in spite of the sharp reduction in energy prices that had taken place in the meantime.

Hollaus, F.; Pollach, G.: Improvement in pulp pressing through controlled infections (German). Zuckerindustrie 111 (1986) pp. 1025-1030.

Abstract: In an effort to reduce the costs of drying pressed beet pulp, particularly high dry solids values are achieved in pulp pressing if, along with technological steps to achieve good pressing, marked bacterial activity occurs in the diffusion system. Since, with continuing uncontrolled infections microbial sugar losses are high and uncontollable, an attemt was made to optimize pulp pressing by "natural acidification" through continuous formalin dosing via a newly developed metering system which provides good distribution of the formalin in tower diffusers. The level of energy consumption for pulp drying (a function of the disinfection conditions) was compared with the costs associated with the controlled infection. Assuming that the total metabolic activity of the bacteria depends on sugar degradation, calculation of the costs for two Austrian sugar factories gave two different results. Whereas, in one case, an adjusted balance between sugar loss and improvement in drying costs occurred at a formalin dosage of 0.005 %, in the other sugar factory the costs of the sugar loss exceeded the energy saving in drying in all the selected variants. The reason for this could perhaps be found in the difference in bacterial populations between the two plants, which is also demonstrated by the different degradation properties of monosaccharides. Further investigations are planned for the 1986 campaign.

Pollach, G.; Wieninger, L.: Investigations on sucrose losses during preliming (French). La sucrerie Belge 99 (1980) pp. 295-301.

Abstract: To obtain data on the level of sucrose losses in preliming, a pilot plant scale Brieghel-Müller preliming trough was installed in a sugar factory and operated with raw juice and milk of lime from the manufacturing process, balances being established for sucrose, glucose, fructose and L- and D-lactic acid. Despite some difficulties with the method in the demonstartion of small sucrose differences, using an enzymatic technique, it could be shown that by disinfection of the extraction plant the preliming could also be rendered more sanitory so that no permanent sucrose decomposition occurred in this region. An aimed disinfection of the preliming, e.g. by additional, supporting doses of formalin injected into the raw juice, permitted progressive preliming, at temperatures of 30°C and higher, to be carried out in such a manner that only a loss commensurate with the limits of detection for the sucrose balance, i.e. approximately 0.3 % on sucrose, need be expected, just before formalin dosage. Based on the experimental results it seems impossible to estimate an actual loss in the preliming from results of glucose, fructose or lactic acid measurement.

Klaushofer, H.; Pollach, G.; Radda, H.: A fully automated equipment for baker's yeast fermentation in the laboratory scale (German). Die Brannweinwirtschaft 120 (1980) pp. 363-368.

Abstract:

Pollach, G.: Microbiological determination of sucrose by means of heterogeneous cultures of Bacillus stearothermophilus (German). Zucker 29 (1976) pp. 427-432; 495-501.

Abstract: A microbiological technique for quantitative determination of sucrose is described which is based on continuous flow analysis. It can be carried out with normal commercial equipment. Diluted samples are mixed with a continuously cultivated pre-culture of sucrose-selective micro-organisms. After incubation in a tubular fermenter they are subjected to continuous pH measurement. In contrast to methods described in previous papers, the advantages lie in the greater analysis frequency (40 per hour) and continuous operation which is independent of test material. The repetability coefficient of variation, obtainable under ideal conditions (matrix-free solution, maximum response), is 0.3-0.4. Systematic errors caused by the sample matrix can be eliminated or reduced by use of an internal standard or additional use of saccharase. Given examples of application include analytical instructions and reference points for determination of method precision and accuracy in individual cases. Within the beet sugar industry the method is suitable for beet, pulp products, juices and syrup, while outside it can be applied to cane molasses, confectionery and honey. The possibility of application in the field of medicine is indicated.

Pollach, G.: Biological determination of sugar content and its application in practice (German). Z. Zuckerindustrie 24 (1974) pp. 633-639.

Abstract: The author describes a method working on a microbiologic basis for determining automatically the sugar content of juices from the field of extraction, especially for the determination of pulp press water sugar content. This is based on conversion into acid of sugars present in samples by thermophilic micro-organisms in sample material and titration of produced acids with nutrient-containing lye. Analytical results are compared in two series of measurement with polarimetric determinations. The author shows that it is possible to apply the method to the analysis of various juices from extraction plants and gives indications concerning the practical use of the method within a regulating concept for beet extraction.

Klaushofer, H.; Pollach, G.: On the problem of sugar losses by highly thermophilic micro-organisms in beet sugar factory. I. Correlation between sugar decomposition and acid formation (German). Zucker 25 (1972) pp. 157-165.

Abstract: The sugar losses caused by microbial acid formation in beet sugar factory diffusers were investigated. The ratio between the quantity of acid formed and the quantity of sugar decomposed was determined for a large number of bacterial strains and cultures in the form of infected diffusion juices in order to be able to calculate sucrose losses from an increase in diffusion juice acids. According to the type of highly thermophilic micro-organism, 0.8 - 1.1 meq of acid was obtained per 100 mg of sugar. Average values given in the literature for mixed cultures of highly thermophilic bacilli are all lower, and in most cases considerable scatter is indicated. Further tests were carried out in an endeavour to find the sugar losses direct from the fall in pH in the diffuser, having regard to the buffering capacity of diffusion juices. To be able to evaluate the quantities of acid discharged with pressed pulp and acting as an extra loss, the buffering capacity of the constituents of such pulp was investigated.

Klaushofer, H.; Pollach, G.: On the problem of sugar losses by highly thermophilic micro-organisms in beet sugar factory. II. Microbial decomposition of reducing sugars (German). Zucker 25 (1972) pp. 388-395.

Abstract: An investigation was carried out to find to what extent microbially formed acids in diffusers originate not from sucrose but from monosaccharides present in the diffusion juice (not formed microbially). The decomposition rates for sucrose, glucose and fructose were compared using pure cultures. It was found that different strains are involved and many act preferentially on monosaccharides, while others decompose sucrose more rapidly than its monosaccharide components. Causes of the differences in decomposition rates might be found, at least partly, by referring to suggestions in earlier published works regarding the presence of an “active transfer“ for the preferentially involved sugar. There is a relationship between the preferential decomposition of a given sugar and other mass transfer properties. A strain of hyperthermophilic bacillus frequently occurs in diffusion juices which primarily decomposes reducing sugars and not sucrose; it is characterized by a marked nitrite-reducing capacity. In the case of infections caused by hyperthermophilic H₂S-forming bacteria, a small proportion of the acids formed by the bacteria result from reducing sugar decomposition.

Klaushofer, H.; Pollach, G.: On the problem of sugar losses by highly thermophilic micro-organisms in beet sugar factory. III. Microbial invert sugar formation and loss balance (German). Zucker 25 (1972) pp. 602-609.

Abstract: The sucrose loss alone calculated from the pH drop in diffusers can sometimes increase considerably as a result of microbial, extracellular formation of invert sugar. Under certain conditions, infections caused by hyperthermophilic bacilli, which can be characterized by their accumulation of nitrite in the juice which they do not re-consume, cause a noticeable increase in invert sugar apart from acid formation. However, infections of this nature are rarely observed in practice. Even among a series of selected strains from a collection of micro-organisms only one representative was found which forms exo-invertase to any greater extent. With infections caused by hyperthermophilic bacteria which form H₂S, any additional loss through microbial formation of invert sugar is not to be expected. The loss components considered in three reports are summarized in a survey and information published to date is compared. In addition, it is shown that knowledge of the sugar loss in individual cases is not needed for optimum disinfection.

Klaushofer, H.; Hollaus, F.; Pollach, G.: Microbiology of Beet Sugar Manufacture. Process Biochemistry (1971) June issue, pp. 39-41.

Abstract:

Pollach, G.; Klaushofer, H.: The direct quantitative determination of sucrose with the aid of Bacillus stearothermophilus (German). Z. Zuckerindustrie 21 (1971) pp. 277-280.

Abstract: A Bacillus stearothermophilus strain shows the special property of decomposing sucrose to acid in a shorter time than other sugars and moreover at a high speed independent of the sucrose concentration. This property is pronounced so as to allow quantitative sucrose determination to be built up on it. The method is not interferred by, for instance, a fiftyfold excess of invert sugar. The chief apparatus needed are a temperable incubation vessel and a recording pH-meter. The analysis proper includes the dosage into an incubation vessel of samples, calibration solutions, and lye, and that without the necessity of sterilising the material, and the reading of the data from the pH-diagram at intervals ranging from about 15 to 30 minutes.