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A Comparative Study of Batch Fermentation Performance of A Comparative Study of Batch Fermentation Performance of

Saccharomyces carlsbengensis and Saccharomyces cerevisiae Saccharomyces carlsbengensis and Saccharomyces cerevisiae

based on Kinetic Parameters based on Kinetic Parameters

Luljeta Pinguli University of Tirana, luljeta.pinguli@fshn.edu.al

Ilirjan Malollari University of Tirana

Anisa Dhroso University of Tirana

Hasime Manaj University of Tirana

Dhurata Premtis University of Tirana

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Recommended Citation Recommended Citation Pinguli, Luljeta; Malollari, Ilirjan; Dhroso, Anisa; Manaj, Hasime; and Premtis, Dhurata, "A Comparative Study of Batch Fermentation Performance of Saccharomyces carlsbengensis and Saccharomyces cerevisiae based on Kinetic Parameters" (2018). UBT International Conference. 159. https://knowledgecenter.ubt-uni.net/conference/2018/all-events/159

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A Comparative Study of Batch Fermentation Performance

of Saccharomyces carlsbengensis and Saccharomyces

cerevisiae based on Kinetic Parameters

Luljeta Pinguli1, Ilirjan Malollari2, Anisa Dhroso3, Hasime Manaj4, Dhurata Premti5

1,2,3,4,5University of Tirana, Faculty of Natural Sciences, Department of Industrial Chemistry, Tirana , Albania

E-mail: luljeta.pinguli@fshn.edu.al

Abstract. Biological systems are very complex regarding their kinetic behavior. There are many models that intend to predict fermentation performance, although Monod equation remains the best model. A detailed investigation of batch fermentation process at room temperature for two different types of yeast Saccharomyces carlsbegensis and Saccharomyces cerevisiae was carried out. Batch fermentation experiments were carried in 1 liter bioreactors, in the same medium, time and fermentation conditions. Kinetic constants were used to compare fermentation performance under similar conditions. Kinetic parameters investigation was done based on growth kinetics, ethanol productivity and substrate consumption (glucose) using computer simulation for different kinetic models. There are some notable differences based on kinetic models. Although two types of yeast strain leave the same remain extract in the end of fermentation, fermentation dynamics

differ from each other. Saccharomyces carlsbengensis has higher ( max and Ks ) kinetic constants compared to Saccharomyces cerevisiae. For both fermentations the best predicting model was Monod, better results give saccharomyces carsbegensis curve.

Keywords: kinetic parameters, model, Sacharomyces carlsbegensis, Saccharomyces cerevisiae, batch fermentation.

1 Introduction

Yeasts have been used by humans to produce foods for thousands of years. Bread,

wine, sake and beer are made with the essential contribution of yeasts, especially from

the species Saccharomyces cerevisiae and Saccharomyces carlsbegensis[1].

Nowadays, modern industries require very large amounts of selected yeasts to obtain

high quality reproducible products and to ensure fast, complete fermentations.

Efficient and profitable factory-scale processes have been developed to produce yeast

biomass. The standard process was empirically optimized to obtain the highest yield

by increasing biomass production and decreasing costs. However in recent years,

several molecular and physiological studies have revealed that yeast undergoes

diverse stressful situations along the biomass production process which can seriously

affect its fermentative capacity and technological performance. Several classic studies

have evaluated the energy, kinetic and yield parameters of the yeast biomass

production process [2],[3]. However, the biochemical and molecular aspects of yeast

adaptation to industrial fermentation conditions have been poorly characterized. In

recent years, a substantial effort has been made to gain insight into yeast responses

during the process. It was believed that fermentation conditions were optimized to

obtain the best performing yeast cells, but now we know that yeast cells endure

several stressful situations that induce multiple intracellular changes and challenge

their technological fitness As a result, these dynamic environmental injuries seriously

affect biomass yield, fermentative capacity, vitality, and cell [4], [5]. This paper

undertakes a study to compare fermentation processes with Sacharomyces

carlsbegensis and Saccharomyces cerevisiae under similar conditions through

evaluations of kinetic parameters.

2 Materials and Methods

There were carried out in parallel in the same conditions batch fermentations in 1 liter bioreactors with two types of yeast strains, bottom brewery yeast strain Saccharomyces carlsbegensis SW 35 and industrial bread yeast Saccharomyces cerevisiae. Cell density used for both parallels were 8% of fermentation medium. Yeast suspensions have almost the same concentration, vitality and generation. After 2 hours in aerobic conditions with moderated stirring, the bioreactors were put in fermentation conditions. There was used different substrate concentration in total 8 parallel trials. As fermentation medium was used beer wort with 16%, 14 %, 12%, 10%, 8%, 7%, 6%, 5% sugar extract. Batch performance was surveyed for up to 48

hours in 200C and at regular intervals of time was taken samples to substrate

concentrations. Tested methods used were standard analyses taken from “Analytica EBC; Methods of Analysis” and “Analytica-EBC Microbiologica” [9], [10]. Kinetic studies based on data gathered from experiment were done based on computer simulation and modeling.

3 Results

Fermentation performance was studied based on substrate consumption curves. Samples were taken into regular intervals until remain extracts remain constant for 24 hours. Figure 1, represent fermentation curves in presence of two yeast strains for different initial substrate concentration batches.

5% 6% 7% 8%

10% 12% 14% 16%

18 16 14 12 10

8

6

4

2

0

0 5 21 24 Fermentation time in hours for S. cerevisiae

5% 6% 7% 8% 10% 12% 14% 16%

18 16 14 12 10

8

6

4

2

0 0 5 10 15 20

Fermentation time in hours for S. carlsbegensis

Fig. 1. Substrate consumption versus fermentation time for different substrate concentration

batches inoculated with two different yeast strains.

Comparing fermentations performances noticed that fermentation with

Saccharomyces cerevisiae is faster for the first hours of fermentation. Final remain

extract in the end of fermentation is proportional to initial wort extract and are almost

the same for parallel batches with different yeast strains.

0.45 S.

0.4

for 0.35

(µ)

0.3

grow

thra

te ce

r

evis

iae

0.15

0.25

Spec

ific

0.2

0.05 0.1

0 0 5 10 15 20 Substrat concentration %

0.4

S.

0.35

f o r

0.3

grow

th ra

te

(µ)c

arlsb

egen

sis

0.25

0.2

0.15

Spe

ci

fic 0.1

0.05

0

0 5 10 15 20 Substrate concentration %

Fig. 2. Substrate concentration (s), versus specific growth rate (µ).

Kinetic constant determination was realised based on linearization curves

Lineweaver-Burk. Figure 3 and 4 represent linearization’s lines. Equations 1-4

represent linearization equations and their values for each figure. 1

Ks

1 1 [1]

max s

max

y 21.05 x 0.921 [2]

max

1 1.0857

[3] 0.921

Ks 21.05 K

s

max 21.05 22.85 [4]

max

7 6 5 4 3 2 1 0

y = 21.05x + 0.921

0 0.05 0.1 1/s 0.15 0.2 0.25

Fig. 3. Lineweaver-Burk linearization for Saccharomyces cerevisiae fermentation.

9 y = 36.917x + 0.6705 8

7

6

1/µ

5

4

3

2

1

0

0 0.05 0.1 0.15 0.2 0.25 1/s

Fig. 4. Lineweaver-Burk linearization for Saccharomyces carlsbegensis fermentation.

Kinetic constants for Saccharomyces carlsbegensis were:

and Ks 55.123

In this paper to compare our experimental model we have used three models. The

well-known Monod model and equations 5 and 6, which represent respectively the

model in a high microbic density and the model wih a varesi from limiting substrate.

max

s [5]

K s x s

max

s [6] K

s

s s 0

max 1.491

1

0.9

cere

sisi

ae 0.8

0.6

0.7

S.

0.5

fo r

( µ ) 0.4

rat

e

0.3

gro

wth

0.2

Spec

if

ic 0.1

0 5 10 15 0

Substrate % (s)

1.2

S.ca

rlsb

egen

sis

1

0.6 0.8

(µ)

for

0.4

rate

grow

th

0.2

Spec

ifi

c

0

0 5 10 15

Substrate % (s)

Fig. 5. Specific growth rate versus substrate concentration for different experimental data’s ( ) Monod model (•••••••••), high density model (

substrate model ( ).

20

20

models

used: ) limiting

4 Conclusions

Study of batch fermentation processes for two different types of yeast strains Saccharomyces carlsbegensis and Saccharomyces cerevisiae gives some results that were confirmed by kinetic parameters also. There were some notable differences based on kinetic models. Although two types of yeast strain leave the same remain

extract in the end of fermentation, fermentation dynamics differ from each other. Saccharomyces cerevisiae ferment faster for the first five hours and later slow down significantly fermentation rate. Brewery yeast has a uniform fermentation rate until

final extract stops. Saccharomyces carlsbengensis has higher ( max and Ks ) kinetic constants compared to Saccharomyces cerevisiae. For both fermentations the best predicting model was Monod, better results give saccharomyces carsbegensis curve.

4 References

1. Reed, G. & Nagodawithana, T. W.: Technology of Yeast Usage in Winemaking. Am. J.

Enol. Vitic., (1988), Vol. 39, No. 1, pp. 83-90. 2. Reed, G. & Nagodawithana, T. W.: Baker's Yeast Production. In: Yeast Technology

(1991), 261-314 3. Beudeker, R.F.; Van Dam H.W.; Van der Plaat, J.B. & Vellenga, K.: Developments in

bakers' yeast production, (1990), 103-146..

4. Blanco, C. A.; Rayo, J. & Giralda, J. M.: Improving industrial full-scale production of

baker's yeast by optimizing aeration control. J.AOAC Int., (2008), Vol. 91, No. 3, pp. 607-

613.

5. Chur, Switzerland. Di Serio, M.; Tesser, R. & Santacesaria, E.: A kinetic and mass transfer

model to simulate the growth of baker's yeast in industrial bioreactors. (2001) Chem. Eng.

J Vol. 82, pp. 347-354.

6. Gibson, B.R.; Lawrence, S.J.; Leclaire, P.R.; Powell, C.D. & Smart, K.A.: Yeast responses

to stresses associated with industrial brewering handling. FEMS Microbiol. Rev., (2007)

Vol 31, No. 5, pp.535-569. 7. Hulse, G.: Yeast Propagation, in Brewing Yeast Fermentation Performance, Second

Edition (ed K. Smart), Blackwell Science, Oxford, UK, (2008), doi:

10.1002/9780470696040.ch23.

8. Maemura, H.; Morimura, S. & Kida K.: Effects of aeration during the cultivation of

pitching yeast on its characteristics during the subsequent fermentation of wort. J Inst

Brew. (1998), Vol. 104, pp. 207–211. 9. Europian Brewing Chemists: (1992). Analytica EBC; Methods of Analysis. 10. Europian Brewing Chemists: Analytica-EBC Microbiologica.