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Gastrointestinal microbiology - part 7

Các mô hình chemostat có thể được chạy bằng cách sử dụng inocula trong hoặc một trong ống nghiệm trạng thái ổn định (tăng trưởng theo cấp số nhân của các vi khuẩn đã ổn định) đạt được với một vài ngày của prefermentation cấy phân hoặc sau một quá trình lên men trước ngắn | 238 Makivuokko and Nurminen different chemostat- and non-chemostat-type models have major structural differences but the batch fermentors are generally similarly structured small-scale bottle fermentors. The chemostat models can be run using inocula in either an in vitro steady-state the exponential growth of the bacterial has stabilized achieved with several days of prefermentation of the fecal inoculum or after a short 16-24 hours pre-fermentation. Batch-Type Simulators The simplest and most commonly used in vitro method in microbiological studies is the use of batch fermentation with intestinal fluid or fecal slurry to study the effects of different added ingredients. These chemostat are typically anaerobically sealed bottles with fecal caecal or rumen material and these models simulate only a certain part of the animal s GIT e.g. mouse cecum or cow s rumen. The transit times of the intestinal fluids through those areas are relatively short and therefore the run-times in batch fermenting simulations range from 2-24 hours 3-7 . The accumulation of fermentation products e.g. SCFAs can change the conditions in the batch fermentation from the microbially balanced starting point to a more competitive environment for the fermentative microbiota thus affecting the in vivo relevance in longer simulations. More complex fermentation models with several vessels and fluid transitions between vessels either continuously or semi-continuously avoid this accumulation of metabolites and depletion of nutrients. Chemostat-Type Simulators The in vitro colon simulators were introduced for the first time in 1981 8 and all models functioning today have a lot in common with this model. Rumney and Rowland reviewed the first decade of in vitro simulators in their excellent article 3 . Of the models reviewed by Rumney and Rowland the Reading model introduced by Gibson and co-workers in 1988 9 revised 1998 by Macfarlane and co-workers 10 is still actively being used and two new interesting