Możliwości wykorzystania niekonwencjonalnych surowców energetycznych do produkcji etanolu (ang.).pdf

ACTA Acta Sci. Pol., Technol. Aliment. 8(4) 2009, 17-24

ISSN 1644-0730 (print) ISSN 1889-9594 (online)

APPLICABILITY OF UNCONVENTIONAL

ENERGY RAW MATERIALS

IN ETHANOL PRODUCTION

Małgorzata Gumienna, Małgorzata Lasik, Zbigniew Czarnecki,

Katarzyna Szambelan

Poznań University of Life Sciences

Background. The difficult position of Polish agriculture, including one of its branches,

i.e. sugar industry, is conducive of search for solutions aiming at an improvement of the

condition of industry. One of the potential solutions in this respect may be to focus on al-

ternative raw materials and search for ways to overcome recession in renewable energy

sources. The aim of this work was to evaluate the possibilities of using non-starchy mate-

rials – sugar materials, without enzymatic treatment for ethanol production using selected

yeast strains.

Material and methods. Sugar beet pulp and thick juice, as a semi product from sugar

beet, were fermented. The efficiency of the process was assessed using two Saccharomy-

ces cerevisiae preparations – Ethanol Red, Fermiol. Fermentation was run for 72 h

at 30°C. Quality of produced raw distillates was evaluated using the GC method.

Results. The research on fermentation processes showed that sugar beet pulp let obtain

higher ethanol yield – 87% of theoretical than sugar beet thick juice – 84% of theoretical,

both for Ethanol Red and Fermiol yeast preparations. Moreover, it was exhibited that the

increase of sugar concentration in the fermentation medium obtained from thick juice, sta-

tistically importantly influenced ethanol yield decrease, for both yeast preparations. The

distillates’ quality analysis showed the influence of raw materials and microorganism

used for fermentation on pollution degree. Distillate obtained from thick juice was charac-

terised with the lowest by-products content after fermentation with Ethanol Red.

Conclusions. The results make additional possibilities for sugar beet utilization in distill-

ery industry and new markets using production surpluses both for sugar beet and its semi-

-product – thick juice.

Key words: bioethanol, sugar beets, fermentation, thick juice

Corresponding author – Adres do korespondencji: Dr inż. Małgorzata Gumienna, Institute of

Food Technology of Plant Origin of Poznań University of Life Sciences, Wojska Polskiego 31,

60-624 Poznań, Poland, e-mail: gumienna@up.poznan.pl

M. Gumienna ...

INTRODUCTION

The difficult position of Polish agriculture, including one of its branches, i.e. sugar

industry, is conducive of search for solutions aiming at an improvement of the condition

of industry. One of the potential solutions in this respect may be to focus on alternative

raw materials and search for ways to overcome recession in renewable energy sources.

Annual economic analyses indicate an increased demand for energy, resulting from the

dynamics of the population growth and an improving economic standard [Rygielski

2002]. Long-term forecasts predict that the continuous increase in the consumption of

natural energy resources will be accompanied by an increasing concentration of CO 2

(the greenhouse effect), thus it is necessary to search for new, alternative sources of

energy, including biomass fuels. Replacement of conventional energy carriers with

biomass fuels results also from supply safety. To ensure feasibility of plant raw material

processing and utilization of mineral raw materials in the production of fuels it is neces-

sary for the energy value of the product to exceed the energy consumption required for

its production [Jolly 2007]. The balance of production of ethanol and plant raw mate-

rials is dependent on the type of the raw material and the applied processing technology.

In the French model thick juice subjected to fermentation is used in bioethanol produc-

tion, with the further technological line resembling the conventional commercial-scale

distillery. In turn, the model used in Italy consists in thickening of raw juice, crystalliza-

tion of raw sugar and fermentation processing of total run-off syrups into ethanol. Other

technologies propose the production of ethanol from thick juice and run-off syrups dur-

ing the sugar campaign, while during the rest of the year – from other raw materials

(potatoes, wheat, maize) [Rygielski 2002]. World economy showed long ago that biofu-

els may compete with conventional fuels. An advantage of raw materials containing

simple sugars and disaccharides, such as sucrose, is their simplified technology of ex-

traction to the water medium, followed by fermentation by microbial strains to ethanol,

without the need of additional technological operations connected with chemical or

enzymatic hydrolysis, increasing costs of biosynthesis [Szopa and Patelski 2006]. Sugar

beets may be processed to spirit using at least two methods: one consisting in the fer-

mentation of juice produced from sugar beets by diffusion, while the other consisting in

the fermentation of liquid mass, obtained from whole sugar beet roots boiled under

pressure in the water medium.

Although the process of spirit biosynthesis by yeasts is relatively well-known, it is

essential to optimize processes of bioethanol production from sugar beet roots, i.e. se-

lect adequate yeast strains, develop conditions of optimal sugar extraction and develop

fermentation conditions. It is advisable for the applied strains to ferment the medium

with a high sugar content and survive higher concentrations of ethanol [Ogbonna et al.

2001, Szopa and Patelski 2006, Grajek et al. 2008, Balcerek and Pielech-Przybylska

2008].

The aim of this study was to search for new, unconventional raw materials in the

production of bioethanol with a simultaneous potential improvement of production

output. The study investigated applicability of non-starch raw materials – mainly con-

taining sugars not requiring enzymatic treatment in the production of ethanol. The fea-

sibility of fermentation of sugar beet pulp and a semi-product produced from sugar

beets, i.e. thick juice, was assessed; moreover, the effect of applied microorganisms

on ethanol yield was investigated.

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Applicability of unconventional energy raw materials in ethanol production

MATERIAL AND METHODS

The experimental material consisted of sugar beet pulp obtained after grinding of

sugar beets, and thick juice – as a semi-product obtained during the technological

process of sugar production from sugar beets. Raw material was obtained from the Opa-

lenica sugar factory and came from the 2007/2008 campaign.

Microorganisms used in this study were yeasts Saccharomyces cerevisiae – prepara-

tions Ethanol Red and Fermiol by Lasaffre (France). Yeasts were used at 0.5 g/kg mash.

Characteristics of used commercial yeast preparations:

– pitching temperature – Ethanol Red (ER – recommended for thick mash) – 32-

-35°C, Fermiol (F) – 32-35°C, while during fermentation it should not exceed

40°C for ER and 38°C for Fermiol

– tolerated ethanol concentrations: Ethanol Red up to 18% alcohol volume, Fermiol

up to 12% alcohol volume.

No additional mineral media for yeast growth were applied during fermentation.

The course of fermentation. The fermentation process was run in Erlenmeyer

flasks of 250 ml, in which 150 g fermentation medium were placed, i.e. sugar beet pulp,

or 100 ml thick juice corresponding to mash density of 10, 16 and 20°Blg. The medium

was inoculated with yeast mother at 10% in relation to the fermenting medium. Fermen-

tation was run for 72 h at 30°C. The course of the process is presented in Figure 1.

Sugar beet-pulp, thick juice

Water

Mixing

pH regulation

5.6-6.0

Pasteurization

100°C, 15 min

S. cerevisiae yeasts

Cooling – 30°C

Inoculation

Fermentation

30°C, time 48 or 72 h

Distillation

Stillage

Distillate

Fig. 1. Ethanol biosynthesis from the beet pulp and thick beet juice

Acta Scientiarum Polonorum, Technologia Alimentaria 8(4) 2009

M. Gumienna ...

Characteristics of raw material and the evaluation of obtained wash were performed

using standard methods and determined total solids of raw material [Kriełowska-Kułas

1993], reducing sugars [Miller 1959], sucrose content by polarimetry [Kriełowska-

-Kułas 1993] and the viability and population size of yeasts in wash were monitored

[Kriełowska-Kułas 1993]. Moreover, ethanol content in wash was determined using

the aerometry method and in order to verify collected results by HPLC as modified by

the authors [Gumienna et al. 2008]. Quality of produced raw distillates was evaluated

using the GC method.

The analysis of variance ANOVA using the Statistica 6.0 software was performed

in order to compare the significance of differences between samples (for α = 0.05).

RESULTS

In the study sugar beet roots were used as well as their semi-product, i.e. thick juice.

The tested raw material was characterized by a high sucrose content, which for sugar

beets was 17%, while for thick juice it was 82%. Original parameters of the experimen-

tal material are listed in Table 1.

In order to determine the effect of the type of applied non-starch raw material and

two commercial yeast preparations, i.e. Fermiol and Ethanol Red, the fermentation

process was run (Tables 2 and 3).

As a result of analyses it was found that there is a significant effect (p  0.05) of

the type of used raw material (fermentation medium) on the yield of ethyl alcohol.

The fermentation medium produced from sugar beet pulp exhibited a higher alcoholic

fermentation efficiency in relation to media produced from thick juice for both applied

yeast preparations.

Table 1. Characteristics of raw material

Material

Dry matter

Reducing substances

mg·cm -3

Sucrose

Sugar beet-pulp

26.52 ±0.17

7.12 ±0.02

4.07 ±0.44

17.27 ±0.03

Thick juice

85.00 ±0.05

8.91 ±0.03

2.34 ±0.30

82.80 ±0.02

Table 2. Ethanol fermentation of sugar beet pulp using two preparations of yeasts

Initial

extract

°Blg

Ethanol yield

Stillage

Mate-

rial

Initial pH

pH after

fermentation

% v/v

dm 3 ·100 kg -1

beet

% of theoret.

yield

red. subst.

mgcm -3

sucrose

Sugar

beet-

-pulp

Saccharomyces cerevisiae yeasts – preparation Ethanol Red

5.57 ±0.07 3.17 ±0.05 5.15 ±0.01 10.30 ±0.01 87.54 ±0.01 1.40 ±0.11 0.00 ±0.0

Saccharomyces cerevisiae yeasts – preparation Fermiol

5.55 ±0.06 3.43 ±0.09 5.15 ±0.01 10.80 ±0.01 87.54 ±1.01 1.05 ±0.37 0.00 ±0.0

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Applicability of unconventional energy raw materials in ethanol production

Table 3. Ethanol fermentation of thick beet juice using two preparations of yeasts

Initial

extract

°Blg

Ethanol yield

Stillage

Mate-

rial

pH after

fermentation

Initial pH

% v/v

dm 3 ·100 kg -1

beet

% of theoret.

yield

red. subst.

mgcm -3

sucrose

Thick

juice

Saccharomyces cerevisiae yeasts – preparation Ethanol Red

5.50 ±0.11 4.53 ±0.09 5.90 ±0.01 47.97 ±0.01 84.77 ±0.11 1.65 ±0.11 0.00 ±0.0

5.53 ±0.01 4.60 ±0.13 5.90 ±0.01 30.57 ±0.65 54.06 ±0.09 28.55 ±2.23 0.00 ±0.0

5.65 ±0.12 4.74 ±0.08 5.15 ±0.01 26.65 ±0.01 37.63 ±0.21 63.87 ±1.43 0.00 ±0.0

Saccharomyces cerevisiae yeasts – preparation Fermiol

5.62 ±0.06 5.24 ±0.25 5.90 ±0.01 48.36 ±0.01 85.38 ±1.79 1.33 ±0.37 0.00 ±0.0

5.50 ±0.50 4.37 ±0.21 7.40 ±0.01 36.60 ±0.04 64.96 ±0.01 14.69 ±3.07 0.00 ±0.0

5.67 ±0.11 4.72 ±0.20 6.65 ±0.01 27.37 ±0.14 65.38 ±0.01 32.03 ±6.76 0.00 ±0.0

The yield of ethyl alcohol produced as a result of sugar beet pulp fermentation

reached the highest value of 87.5% in relation to the theoretical yield for a medium with

a density of 10°Blg both for Ethanol Red and Fermiol (Table 2). In case of fermentation

media, where thick juice was used, the highest yield of approx. 85% in relation to the

theoretical yield was also obtained for a density of 10°Blg. At the same time it was

found that the type of the applied preparation did not have a significant effect (p  0.05)

on recorded yield of ethanol (Table 3). However, the application of thick juice as a sub-

strate for the production of ethanol showed a significant reduction (p  0.05) of percen-

tage theoretical yield of alcohol with an increase in the concentration of sugar (mash

density of 16-20°Blg) in the medium for both applied preparations (Table 3).

Table 4. The concentration of contaminations in distillates obtained after fermentation of sugar

beet pulp and thick juice, g·dm -3 of 100% spirit

Material

Extract

°Blg

Aldehyde

Fusel oil

Methanol

Sugar beet-pulp

Saccharomyces cerevisiae yeasts – preparation Ethanol Red

0.062 ±0.011 0.028 ±0.002 0.062 ±0.002

Saccharomyces cerevisiae yeasts – preparation Fermiol

0.419 ±0.022

1.433 ±0.041

0.700 ±0.021

Thick juice

Saccharomyces cerevisiae yeasts – preparation Ethanol Red

0.015 ±0.001

0.48 ±0.005

0.051 ±0.002

0.079 ±0.010

0.23 ±0.002

0.013 ±0.001

0.007 ±0.001 0.50 ±0.001 0.040 ±0.001

Saccharomyces cerevisiae yeasts – preparation Fermiol

0.035 ±0.002

0.015 ±0.001

0.009 ±0.000

0.135 ±0.061

0.157 ±0.032

0.006 ±0.000

0.189 ±0.032

0.218 ±0.015

0.007 ±0.001

Acta Scientiarum Polonorum, Technologia Alimentaria 8(4) 2009

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