Sterilization of oils: Data to support the use of a continuous point-of-use sterilizer

The continuous slow feed of animal and vegetable oils is frequently found to be an economically attractive method for maintaining antibiotic fermentations at a highly productive rate. The sterilization of oil feeds can present a major problem in the production plant. In this article, we present data and methodology on the kinetics of the thermal sterilization of No. 2 lard oil and soybean oil. It was also determined that dry heat sterilization condition could occur if dry spores were added to dry oil. This condition could only be partially alleviated by the addition of water to the oil. The theory and design of a small tubular coil continuous sterilizer for sterilizing oils at the point of use is also presented. This type of sterilizer is economical and versatile and simplifies control and instrument requirements. It provides a realistic alternative to the use of sterile feed tanks and sterile headers.     

溴甲烷土壤灭菌对大豆苗期根系生长的影响

利用溴甲烷田间土壤灭菌,研究灭菌对正茬、重茬大豆苗期根系生长和产量的影响.试验结果表明,灭菌处理后重茬(连续种植3a)地大豆根系生长良好,根系形态明显改善,总根长、主根长、植株鲜重和根瘤数增加、孢囊线虫孢囊数为0.而灭菌处理后,正茬地大豆根系前期生长受到一定抑制,主根长、总根长、植株鲜重和侧根数有降低的趋势,但随时间推移,抑制幅度降低.溴甲烷处理促进大豆结瘤.灭菌后,重茬大豆与正茬大豆根系生长差异减少.溴甲烷灭菌处理可作为克服大豆连作障碍问题措施之一.     

X-ray sterilization of biopharmaceutical manufacturing equipment—Extractables profile of a film material and copolyester Tritan™ compared to gamma irradiation

The biopharmaceutical industry gains enormous flexibility in production processes by using sterilized preassembled single-use devices. Gamma irradiation is an established sterilization technology that may be restricted in the future by the availability of ⁶⁰Co as irradiation source and irradiation capacities. X-ray technology is considered an alternative type of radiation for sterilizing SU equipment. In the context of extractables and leachables—one concern connected with the use of single-use process equipment—the effect of X-ray irradiation on the extractables profile of the materials needs to be compared to established gamma irradiation to qualify this alternative technology. An approach is presented to obtain robust and comprehensive extractables data for materials used in SU devices after sterilization either using X-ray or gamma irradiation. A careful selection of the test items and the test design allows a one-to-one comparison of data obtained from a combination of orthogonal analytical techniques. The extractables of a modern SU film material and the copolyester Tritan™ are evaluated. The data presented allow a risk evaluation on the safety of this new sterilization modality for biopharmaceutical applications. It is demonstrated that the extractables profile of a polymer is not affected by the type of irradiation used for sterilization.     

Poststerilization regret among women: methodological considerations for the next decade

The literature concerning regret among women following voluntary sterilization shows a lack of methodological rigor. This paper reviews the 7 prospective studies of voluntary sterilization conducted since 1973 that are judged to have adequate design and measurement standards, and suggests methodological considerations for future research. 3 of the studies were conducted in the US, 2 in the UK, 1 in Thailand, and 1 in Pakistan. Only 3 of the 7 studies used control groups and only 3 used standardized pre- and posttest psychological measures. Subjects in all the studies requested sterilization on a voluntary basis. 4 of the 7 studies evaluated contraceptive and menstrual histories before and after sterilization. All the studies varied in their poststerilization follow-up intervals ranging from 2 months and 1 year to 18 months and 2 years. Attrition rates also varied widely across the studies. Although none of these studies presented percentages for precise measures of regret, the overall effect of the sterilization procedure was found to be positive. The relationship between regret and purported indicators of regret, such as depression, anxiety, menstrual difficulties, and desire for reversal, should be documented in prospective, controlled studies. Longer poststerilization follow-up periods are recommended. Responses of childless women and male partners to sterilization should also be considered in future studies. Finally, since repeated references are made to menstrual problems following voluntary sterilization, it is important that studies assessing poststerilization responses control for oral contraceptive (OC) use because OCs reduce menstrual flow and their discontinuation results in a return to normal, although heavier, menstrual flow.     

Complete design analysis of a continuous sterilizer for fermentation media containing suspended solids

An improved mathematical model was developed to design a continuous sterilizer for liquid fermentation media containing suspended solids. Unsteady-state energy balances were used to determine the temperature distribution in the liquid medium and in the solid particles as a function of time and position within the particle, as the medium flows through the sterilizer. Such temperature profiles were used to determine the level of microbial reduction achieved by each component of the sterilizer and by the entire sterilization process. A considerable difference exists between the temperature in the particle core and in the surrounding liquid. This has a significant impact on the degree of sterility achieved by the process. The level of microbial reduction in the particles was found to be tens and or even hundreds of order of magnitude lower than the corresponding level achieved in the liquid. The role of the particle material on the degree of sterilization was also investigated. Solid materials typically found in fermentation media, such as wood or flour clumps were found to offer considerable resistance to the sterilization of the organisms lodged inside them. (c) 1993 Wiley & Sons, Inc.     

A next generation, pilot-scale continuous sterilization system for fermentation media

A new continuous sterilization system was designed, constructed, started up, and qualified for media sterilization for secondary metabolite cultivations, bioconversions, and enzyme production. An existing Honeywell Total Distributed Control 3000-based control system was extended using redundant High performance Process Manager controllers for 98 I/O (input/output) points. This new equipment was retrofitted into an industrial research fermentation pilot plant, designed and constructed in the early 1980s. Design strategies of this new continuous sterilizer system and the expanded control system are described and compared with the literature (including dairy and bio-waste inactivation applications) and the weaknesses of the prior installation for expected effectiveness. In addition, the reasoning behind selection of some of these improved features has been incorporated. Examples of enhancements adopted include sanitary heat exchanger (HEX) design, incorporation of a “flash” cooling HEX, on-line calculation of F _o and R _o, and use of field I/O modules located near the vessel to permit low-cost addition of new instrumentation. Sterilizer performance also was characterized over the expected range of operating conditions. Differences between design and observed temperature, pressure, and other profiles were quantified and investigated.     

Opportunities for the application of real-time bacterial cell analysis using flow cytometry for the advancement of sterilization microbiology

Medical devices provide critical care and diagnostic applications through patient contact. Sterility assurance level (SAL) may be defined as the probability of a single viable micro-organism occurring on an item after a sterilization process. Sterilization microbiology often relies upon using an overkill validation method where a 12-log reduction in recalcitrant bacterial endospore population occurs during the process that exploits conventional laboratory-based culture media for enumeration. This timely review explores key assumptions underpinning use of conventional culture-based methods in sterilization microbiology. Consideration is given to how such methods may limit the ability to fully appreciate the inactivation kinetics of a sterilization process such as vaporized hydrogen peroxide (VH2O2) sterilization, and consequently design efficient sterilization processes. Specific use of the real-time flow cytometry (FCM) is described by way of elucidating the practical relevance of these limitation factors with implications and opportunities for the sterilization industry discussed. Application of FCM to address these culture-based limitation factors will inform real-time kinetic inactivation modelling and unlock potential to embrace emerging opportunities for pharma, medical device and sterilization industries including potentially disruptive applications that may involve reduced usage of sterilant.     

Selection of microbial mutants tolerant to extreme environmental stress using continuous culture-control design

The design of controllers for a continuous selection technique (BOICS; Brown and Oliver, 1982) is considered. This technique is used to obtain microbial mutants that are tolerant to extreme environmental stress. Applications of BOICS have been hampered by the problem of controller design. In this paper, a modified implementation of BOICS is considered which has a number of practical advantages. A model-based approach to controller design is taken. The case in which the stress is due to an inhibitory substance in the growth environment is considered. The analysis is intended to be applicable to any reasonable combination of organism and inhibitor. Conventional linear and time-invariant controllers are considered. Guidelines for the selection of controller parameters' values are suggested. The application of these guidelines requires that certain process parameters' values be identified. Methods by which these parameters' values can be identified are suggested. Simulation results indicate that the resulting controllers perform satisfactorily. This is confirmed by experimental data from a model selection experiment. A recipe for the design of controllers is a necessary part of a protocol for BOICS. It is hoped that the solution to the controller design problem that is offered in this paper will encourage further applications for the technique.     

土壤灭菌对辣椒抗连作障碍效果

采用土壤灭菌的方法研究了生物因素对连作3年的辣椒植株生长发育和抗氧化酶活性的影响。探讨了土壤灭菌对辣椒抗连作障碍的效果。结果表明,灭菌的连作土壤,辣椒的株高、茎粗、叶面积、叶绿素含量、地上部鲜重、根鲜重、根系活力等值均高于未灭菌土壤,并伴随着抗氧化酶如超氧化物歧化酶（SOD）和过氧化物酶（POD）的活性降低。说明土壤灭菌提高了地上部和根的健壮程度．降低了连作辣椒中抗氧化酶的活性。与正茬土壤相比,辣椒植株的健壮程度仍存在明显差异,抗氧化酶SOD和POD的活性偏高,这可能是短期连作中,土壤灭菌有效的克服了有害微生物的连作障碍效应,但是不能消除由化感物质引起的连作障碍效应。     

Adaptive Dc-optimal designs for dose finding based on a continuous efficacy endpoint

We introduce a new optimal design for dose finding with a continuous efficacy endpoint. This design is studied in the context of a flexible model for the mean of the dose-response. The design incorporates aspects of both D- and c-optimality and can be used when the study goals under consideration include dose-response estimation, followed by identification of the target dose. Different optimality criteria are considered. Simulations are shown with results comparing our adaptive design to the fixed allocation (without adaptations). We show that both the estimation of dose-response and identification of the minimum effective dose are improved using our design.     

Heat Generation and its Impact on Lamp Fouling During Cheese Whey Sterilization using Ultraviolet Radiation

Summary In previous studies we found that lamp fouling was a major limitation when tubular ultraviolet reactors were used for sterilization of cheese whey over an extended period of time. Heat generation by ultraviolet lamps causes the temperature of the flowing fluid to rise and thus enhances fouling. In this study, the heat generated by a low pressure mercury ultraviolet lamp during continuous sterilization of cheese whey in three tubular reactors having different gap sizes (18, 13 and 6 mm) was calculated using a heat balance formula. The technique quantified the heat produced in and lost from each reactor. The heat balance calculations showed that lamp heat generation decreased with decreasing gap size (50.48, 47.71 and 31.91 kJ/h for 18, 13 and 6 mm gap sizes, respectively). However, the heat gain per unit volume and consequently the steady state temperature of the cheese whey effluent increased with decreasing gap size (91.79, 159.03 and 319.12 kJ/l and 44.5, 53.4 and 62.8 °C for 18, 13 and 6 mm gap sizes, respectively). A strong correlation between the amount of heat gain per unit volume and the amount of fouling material accumulated on the quartz surface was realized. The amount of accumulated fouling material increased with decreasing gap size (14.42, 15.31 and 25.26 g on wet basis for 18, 13 and 6 mm gap sizes, respectively). A new design in which the direct contact between the lamp and the flowing cheese whey is avoided and lamp cooling is introduced should be investigated.     

Human-cat relationship in an oceanic biosphere reserve: The case of La Palma Island,Canary archipelago

Removal of feral cats from island environments is a useful mechanism by which their ecological impact on endangered species can be reduced or ended. Nevertheless, because cats are anthropogenic in their origins, social perceptions of management practices play a large role in their implementation. Four-hundred questionnaires were delivered (386 were returned) with 100 going to each of the following: local residents; environmental workers; tourists; and, hunters. Questions explored respondents’ knowledge about island biodiversity and invasive species as well as attitudes towards cat population management methods. Habitat destruction and introduction of invasive species were considered the main threats for the conservation of island biodiversity. Most respondents considered cats to have a negative impact on biodiversity and sterilization campaigns were considered most appropriate for cat population control. Several free sterilization campaigns have been conducted in La Palma Island Biosphere Reserve in order to reduce free-ranging cats and were well received by local people. This research, which combined concepts of management, ecology and social sciences, provides valuable insights which may to be applicable on several other islands where cats and people are present and in conflict with conservation priorities.     

Improvement of a Continuous-Culture Apparatus for Long-Term Use

A glass and plastic apparatus was designed to meet requirements for continuous culture of cells. Some of the improvements incorporated into this apparatus include an all-glass growth vessel with a self-cleaning bottom, special compression fittings to connect tubing to glass tubing, a removable yield reservoir, and a nonwetting gas exhaust assembly. All portions of the system can be autoclaved for sterilization, and medium bottles and pump lines are replaced aseptically.     

Continuous ethanol production from concentrated wood hydrolysates in an internal membrane-filtration bioreactor

Continuous culture for the production of ethanol from wood hydrolysate was carried out in an internal membrane-filtration bioreactor. The hydrolysate medium was sterilized at a relatively low temperature of 60 degrees C with the intention of reducing the formation of inhibitory compounds during the sterilization. The maximum ethanol concentration and productivity obtained in this study were 76.9 g/L and 16.9 g/L-h, respectively, which were much higher than those (57.2-67 g/L and 0.3-1.0 g/L-h) obtained in batch cultures using hydrolysate media sterilized at 60 degrees C. The productivity was also found to be much higher than that (6.7 g/L-h) obtained in a continuous cell retention culture using a wood hydrolysate sterilized at 121 degrees C. These results show that the internal membrane-filtration bioreactor in combination with low-temperature sterilization could be very effective for ethanol production from wood hydrolysate.     

Output stabilization of fermentation processes: A binary control system approach

Two types of continuous fermentation processes for product formation are considered. The processes are described by three nonlinear differential equations with uncertain parameters. Binary control design for theses processes is proposed. The asymptotic output stabilization problems are solved. The control design is carried out with direct use of nonlinear model and microbiological expert knowledge. The good system robustness to parameter uncertainties and external disturbance is demonstrated by simulation investigations.     

Plasma-Mediated Inactivation of Pseudomonas aeruginosa Biofilms Grown on Borosilicate Surfaces under Continuous Culture System

Biofilms are microbial communities attached to a surface and embedded in a matrix composed of exopolysaccharides and excreted nucleic acids. Bacterial biofilms are responsible for undesirable effects such as disease, prostheses colonization, biofouling, equipment damage, and pipe plugging. Biofilms are also more resilient than free-living cells to regular sterilization methods and therefore it is indispensable to develop better ways to control and remove them. The use of gas discharge plasmas is a good alternative since plasmas contain a mixture of reactive agents well-known for their decontamination potential against free microorganisms. We have previously reported that Pseudomonas aeruginosa biofilms were inactivated after a 1-min plasma exposure. We determined that the adhesiveness and the thickness of Pseudomonas biofilms grown on borosilicate were reduced. We also reported sequential morphological changes and loss of viability upon plasma treatment. However, the studies were carried out in batch cultures. The use of a continuous culture results in a more homogenous environment ensuring reproducible biofilm growth. The aim of this work was to study plasma-mediated inactivation of P. aeruginosa biofilms grown on borosilicate in a continuous culture system. In this paper we show that biofilms grown on glass under continuous culture can be inactivated by using gas discharge plasma. Both biofilm architecture and cell culturabilty are impacted by the plasma treatment. The inactivation kinetics is similar to previously described ones and cells go through sequential changes ranging from minimal modification without loss of viability at short plasma exposure times, to major structure and viability loss at longer exposure times. We report that changes in biofilm structure leading to the loss of culturability and viability are related to a decrease of the biofilm matrix adhesiveness. To our knowledge, there has been no attempt to evaluate the inactivation/sterilization of biofilms grown in a continuous system.     

Dynamics of heat destruction of spores: A new view

Summary Discrepancies between actual, viable spore populations and those predicted by a classical model during heat sterilization of food and pharmaceutical products have long concerned food engineers and scientists as they pursue new sterilization techniques, including ultra-high temperature processes. Among potential causes of those discrepancies, activation of dormant spores is significant, and models addressing that factor were developed recently. This paper reviews historic and current views on the biology and models of microbial spore populations during heat sterilization. Activation and inactivation of viable spores are emphasized, with each viewed as a first-order reaction. Rate constants of those reactions may differ significantly, inactivation rates of dormant and activated spores may differ, and variations of all rate constants with temperature appear to be well described by Arrhenius equations. Model-based analyses show how categories of survivor response curves observed during isothermal heat treatments can arise from simultaneous activation and inactivation of spores in an overall population. Effects of different distributions of initial subpopulations, different distributions of rate constants, and heat shock for homogenizing an indicator population are shown. The complexity of new, multiple process models has not increased greatly, but the potential for accurate, dynamic prediction of product safety after prescribed sterilization has. The relevant biology is understood and accounted for more thoroughly, and it is anticipated that the new models will aid design and evaluation of new and improved sterilization processes for food and pharmaceuticals.Mention of brand or firm names does not constitute an endorsement by the US Department of Agriculture over others of a similar nature not mentioned.     

Modeling transport processes in sterilization-in-place.

SIP (sterilization-in-place) of equipment using saturated steam is limited by transport processes that restrict the distribution of sterilizing steam. The following are two crucial operations: the removal of air prior to sterilization, and the removal of condensate during the sterilization. Using simple model systems of pipes and tanks, characteristic operating parameters were examined and steady-state models were analyzed. The results were used to evaluate design aspects of SIP, including heat insulation, spacing of steam traps, sloping of lines, steam velocities and consumption, placement of temperature sensors, and scale factors in piping. A more reliable SIP design is achievable by insulating equipment, spacing steam traps to limit condensate buildup, providing an effective air removal operation, and providing reliable, high-quality steam.     

Optimization of batch fermentor sterilization

This article presents a calculation procedure useful for the optimization and scale up of batch sterilization cycles in large-scale fermentors. This technique determines the sterilization temperature and hold-time necessary to minimize nutrient damage in a specific fermentor. The method can also be used for "scaledown" experiments to eliminate sterilization conditions as a scale up parameter. A method for the systematic evaluation of different sterilization conditions on product yield is also presented. This procedure is useful in determining if scale up of sterilization conditions is important for a given process. The validity of the techniques presented are supported by data showing significant yield improvements in a 1.2 x 10(5) L antibiotic fermentation.