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Author:Uuksulainen, Tuomas
Title:pH- ja lämpötilagradienttien vaikutus Lactobacillus rhamnosus GG:n kasvuun ja elävyyteen
The effect of temperature and pH gradients on the viability and growth of Lactobacillus rhamnosus GG
Publication type:Master's thesis
Publication year:2010
Pages:vi + 70 + [21]      Language:   fin
Department/School:Biotekniikan ja kemian tekniikan laitos
Main subject:Bioprosessitekniikka   (Kem-70)
Supervisor:Leisola, Matti
Instructor:Eerikäinen, Tero ; Salonen, Kalle
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  3431   | Archive
Keywords:probiotics
Lactobacillus rhamnosus GG
pH gradients
temperature gradients
scale down
probiootit
Lactobacillus rhamnosus GG
pH-gradientit
lämpötilagradientit
scale-down
Abstract (eng): Production process of probiotic functional foods has high technological demands, because probiotics have to maintain viability after production steps and eventually survive also in the human gastrointestinal tract.
Cultivation conditions form the basis for active and stable probiotic cultures.
In this work the effect of pH and temperature gradients on growth of L.rhamnosus GG probiotic were studied.
In addition their survival during freeze-drying and formulation into product were examined.

pH and temperature gradients were simulated in a laboratory scale by a scale down methodology which enables to mimic hydrodynamic conditions of an industrial scale.
The experimental set up of scale down system consisted of a bioreactor (temperature 37 °C, pH 5.4) and a plug flow reactor.
The temperature (in range of 32-37 °C) and pH (in range of 5.4-6.2) fluctuations were caused into the plug flow reactor.
Industrial growth media were used in the experiments.
In the scale down experiments a chemostat set was used, which allowed studying pH and temperature fluctuation effects under steady state conditions. pH fluctuations were studied also in batch cultivations by changing the set point of the controller.
The survival during the freeze-drying was studied by freezing the cells.
Furthermore cells' viability was evaluated during food formulation by exposing cells to apple juice and to its effective agent malic acid.

Exposal to a transient temperature fluctuation (>1°C and 60 sec.) reduced the amount of viable cells. pH fluctuation (0,2-0,7 pH units) raised the survival of the cells during the freezing marginally, but large temperature fluctuation (>2°C) reduced the survival.
Both temperature and pH fluctuations raised the LGG's survival at the low pH of malic acid solution.
Abstract (fin): Probioottisten elintarvikkeiden tuotanto on teknisesti haastavaa, sillä probioottisten bakteereiden täytyy säilyä elävinä kaikkien tuotantovaiheiden läpi ja lopulta myös kuluttajan ruoansulatusjärjestelmässä.
Kasvatusolosuhteet luovat perustan aktiivisille ja kestäville probioottiviljelmille.
Tässä työssä tutkittiin tuotantomittakaavan bioreaktorin rajallisesta sekoitustehosta aiheutuvien pH- ja lämpötilagradienttien vaikutusta L. rhamnosus GG-solujen (LGG) kasvuun sekä selviytymiseen kylmäkuivauksessa ja tuotteeseen formuloinnissa.

Työssä simuloitiin pH- ja lämpötilagradientteja laboratoriossa scale-downmenetelmällä, jolla voidaan jäljitellä tuotantomittakaavan bioreaktorin hydrodynaamisia olosuhteita.
Scale-down-laitteisto koostui bioreaktorista (lämpötila 37 °C ja pH 5,4) ja tulppavirtausreaktorista, jossa tehtiin lämpötilamuutoksia alueella 32-37 °C ja pH-muutoksia alueella 5,4-6,2.
Kokeissa käytettiin teollista tuotantoalustaa.
Scale-down-kokeet tehtiin kemostaattikasvatuksena kasvuolosuhteiden vakioimiseksi, jotta muutosten vaikutukset saatiin paremmin esiin.
Scale-down-kokeiden lisäksi pH:n vaihtelun vaikutusta tutkittiin panoskasvatuksilla muuttamalla pH:n asetusarvoa ajan funktiona.
Solujen kestävyys kylmäkuivausta kohtaan määritettiin pakastuksella ja selviytyminen formuloinnista omenamehuun ja omenahappoliuokseen.

Hetkellinen (60 s) lämpötilamuutos (>1 °C) laski elävien solujen määrää. pH-muutos (0,2-0,7 pH-yksikköä) paransi marginaalisesti solujen kestävyyttä pakastusta kohtaan, kun taas suurempi lämpötilamuutos (>2 °C) heikensi kestävyyttä.
Sekä pH- että lämpötilamuutokset paransivat LGG:n selviytymistä omenahappoliuoksen alhaisessa pH:ssa.
ED:2010-06-02
INSSI record number: 39702
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