Available via license: CC BY 3.0
Content may be subject to copyright.
IOP Conference Series: Earth and Environmental Science
PAPER • OPEN ACCESS
Utilization of wastes from grain processing industries
To cite this article: S Efremova et al 2019 IOP Conf. Ser.: Earth Environ. Sci. 337 012033
View the article online for updates and enhancements.
This content was downloaded from IP address 38.131.159.187 on 16/11/2019 at 17:14
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
1
Utilization of wastes from grain processing industries
S Efremova1*, Ye Kulikova 2, V Konovalov3 and N A Politaeva4
1Department of biotechnology and tehnosfernaja safety, Penza State Technological
University, Penza, 1A/11 proyezd Baydukova/Gagarina street, Penza 440039 Russia,
2Department of plant breeding, seed production and plant biology, Penza State
Agrarian University, Penza State Agrarian University, Penza, 30 Batanichtskaj street,
440014 Russia,
3Department of Machine Building Technology, Penza State Technological University,
1A/11 proyezd Baydukova/Gagarina street, Penza, 440039 Russia,
4Saint Petersburg State Polytechnical University named after Peter the Great, Saint
Petersburg, Russia
* Corresponding author: efremova_s15@mail.ru
Abstract. Waste materials resulting from the grain processing industries are harmless and easily
amenable to enzymatic and microbial bioconversions. Basidiomycetous mushrooms grown in
vitro are promising producers of protein and essential amino acids. Mushroom biomass
production under appropriate cultivation conditions using agricultural by-products is a cheap and
affordable way to obtain a high-quality food product. The present work explores the possibility
of using grain wastes for the cultivation of golden oyster mushrooms under deep cultivation
conditions. For these purposes, cornmeal was used as a source of carbon waste and gluten as a
source of nitrogen. A high substrate colonization rate was observed. The fruiting cycle lasted
about 26 to 28 days on the studied substrates. The most prolonged cycles were obtained on the
medium supplemented with sawdust. The maximum and the minimum yields were obtained on
wheat straw substrate (171.2 g per kg of substrate) and a grain waste substrate (113.4 g per kg)
respectively. On birch sawdust subtrate and on a substrate of grain waste and birch sawdust
mixture, the yields reached 143.2 g and 130.3 g in this order. The average yielding crop attained
113.4 g of fresh mushrooms grown on 1 kg of substrate under a relative humidity of 70-75%.
This promising work stream not only proposes a waste disposal method, but also, a significant
source of income for the grain processing enterprises.
1. Introduction
The increasing economic growth rate of the agriculture and food industry has aggravated the problem
of waste management, including grain wastes disposal [1, 2].
Waste materials resulting from the grain processing industries are harmless and easily amenable to
enzymatic and microbial bioconversions as well as to various types of preprocessing [3, 4]. Therefore,
it would be relevant to continue exploring this research area.
Bioconversion is a natural way to utilize cellulosic waste. It is based on the destruction of an organic
substrate by microorganisms and fungi. In this way, it allows to solve two main tasks: the creation of an
economically advantageous production process of a target product and, a method of waste disposal for
potential environmental pollutants [5 -7].
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
2
According to the study of mushroom growing techniques worldwide, different types of wastes are
used for substrate preparation, among which: corn stalks, cabbage stalks, rice straw, sunflower husks,
coconut shells, cotton and wood processing waste. For the growth of oyster mushrooms, mixtures of
straw, soybeans, flax, potato peel, cocoa bean processing waste, sugar cane, coffee, tobacco and grapes
are also used as a substrate [8 - 12]. In previous studies, industrial waste has been successfully used for
the cultivation of blue oyster mushrooms. In fact, the use of cardboard as a substrate not only increased
the growth yields, but also provided greater biological efficiency correlated with a greater productivity
of mushroom with larger cap diameter [13].
Under the same cultivation conditions, the spawn rate of oyster mushrooms on substrate dry weight
basis will differ depending on the used substrate [14]. In previous studies, winter wheat straw provided
a yield of 64.6% of fruiting bodies, corncobs - 46.7%; cotton waste - 68.4%; cotton waste and straw
(4:1) mixtrure - 75.8% [15-18].
The main substrate that could be used for the cultivation of oyster mushrooms are wastes such as
vegetable wastes from the agriculture industry. However, in order to expand the resource base of
industrial production of mycelium of higher fungi and to increase the yield of a biomass enriched with
protein, deep cultivation on starch containing plant substrates, including grain waste, is proposed. Yet,
grain waste requires a mandatory pretreatment using acid or enzymatic hydrolysis [19].
The pretreatment of raw materials contributes directly to an increase in the yield of mycelium and its
protein content. Enzymatic hydrolysis is an environmentally friendly process, since there is no threat to
human health. On the other hand, acid hydrolysis requires the use of strong inorganic acids that emit
harmful emanations. In this regard, grain processing wastes were pretreated using "Alfalad" and
"Glyukolad" enzyme preparations produced by Ladyzhensky factory.
Basidial mushrooms grown under artificial conditions (including Pleurotus ostreatus) are promising
producers of environmentally friendly proteins and essential amino acids. Mushroom biomass
production using deep cultivation conditions with the optimal growth environment and favorable
nutritional medium, is a cheap and affordable way to obtain high-quality food products [19]. The
mycelium of the Pleurotus genus cultivated on liquid nutritional medium contains 40-50% of crude
protein and 30-40% of true protein. These proteins are considered valuable biological compounds and
are characterized by a good digestibility, and the mycelium contains all the essential amino acids. The
digestibility of proteins of mushroom biomass obtained by deep cultivation represents 59.3-79.4%.
Thus, one of the potential plant substrates for mushroom cultivation is starch-containing grain waste
from the grain processing industry. Therefore, the purpose of this work is to study the potential use of
grain waste for the cultivation of golden oyster mushroom (Pleurotus citrinopileatus).
2. Methods
The study of the use of grain waste for the cultivation of golden oyster mushroom (Pleurotus
citrinopileatus) was carried out in laboratory conditions with the following experiment scheme: 1.
Control - wheat straw; 2. Grain waste; 3. Grain waste + birch sawdust (in equal proportions); 4. Birch
sawdust. The experiment was performed in triplicate.
The studied substrates were filled into cotton bags and placed in fermentation tanks at a temperature
of 60–70º C for 23–24 hours while basifying water with quicklime at a rate of 0.7–1 kg per 100 liters of
water. After that, the substrates were autoclaved. Oyster mushroom mycelium was inoculated after
cooling the substrate to 28º C [19]. The object of this study was the mycelial culture of golden oyster
mushroom.
The grain spawn planting was performed by uniform mixing with the substrate (moistened to 70%)
in the amount of 3% by weight. Then, polyethylene bags were tightly packed, tied and placed in a
thermostat environment at + 25º C to colonize the substrate with mycelium. After that, 6 cuts of 4-5 cm
longs were made with a sterile scalpel in a staggered manner along the entire length of the bags. The
bags overgrown with mycelium were placed in a room where humidity was maintained at 85-90% and
the temperature between + 18º and 19º C under natural light. Water tanks and a fan were used in order
to maintain the high humidity in the room. At the beginning of the mushroom fruiting, the actively
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
3
liberated carbon dioxide was removed from the room by aerating and turning on the fan. During the
month, we monitored The growth, fruiting bodies formation and the yield of goldenoyster mushroom
Pleurotus citrinopileatus were monitored for a month [15–17].
If infected sites appeared in the bags, they were removed and treated with a solution of sodium
chloride at 250 g/1 liter of hot water [22].
3. Results and observations
Wastes of the grain processing industry include: bran, wastes associated with the cleaning and sorting
of grain mass (grain waste), grain weed impurity, injured grains, feeble and germinated grains, seeds of
wild plants, substandard grains [21].
During the analysis of the studied grain processing wastes, we isolated two fractions: a fraction with
a predominant starch content and another with a predominant fiber content (Table 1). The starch-
containing fraction represented 58.2% in 1 kg of waste, and, the fraction containing a predominance of
fiber - 41.8% by weight in 1 kg of waste.
Table 1. Physical composition of wastes
Fraction Fraction composition Content in 1 kg
of waste, %
Predominantly starchy Grain waste, damaged grains, puny and sprouted
grains, wi
ld plants
seeds
, substandard grains
58,2
With a predominance of
fiber
Bran, chaff, remnants of straw and weeds 41,8
Substrates for mushroom cultivation must have a number of properties, most important of which are
biotechnological - first of all, the ability of the substrate to meet the nutritional needs of the mushroom.
Easily available substances are less significant for oyster mushrooms than for its competitor, mold
fungi; especially in the first days after grain spawn planting. Oyster mushroom refers to fungi that are
equally capable of destruction, both cellulose and lignin, which are highly resistant to biodegradation.
Among the competitors of the oyster mushroom, a special place is given to such fungi as Trichoderma
green mold. In the course of its vital activity, it can utilize cellulose and very quickly develop on
substrates in the presence of easily accessible nutrients.
The selectivity of the substrate is one of the most important biological properties. It is determined by
the chemical composition of the raw material and accordingly, by the activity of the beneficial
microflora located on its surface. The biological selectivity of a substrate is the ability of a thermo-
treated substrate to acquire the most favorable conditions for the development of oyster mushrooms and
to put the competitive microflora into an inactive state.
In various degrees, any type of vegetal raw material may acquire these properties that are of key
importance for the production process. The biochemical mechanism of the acquisition of selective
properties by substrates is based on a change in the substrate content in readily available sugars. The
effect high-temperature on the substrate leads, upon prolonged exposure, to the chemical hydrolysis of
polysaccharides and the accumulation of readily available substances and principally sugars.
When selecting the appropriate substrate for the cultivation of basidiomycetes, a great attention is
paid to the carbon and nitrogen contents. The most suitable substrates are hay clover, wheat straw and
sunflower husk. Grain waste requires the conversion of its polysaccharide complexes into easily
digestible di- and monosaccharides in order to increase its protein content. This is achievable for
example, by acid or enzymatic hydrolysis [6] as well as thermal or chemical treatments of the substrate
for the suppression of the microflora development.
A comparative analysis of the chemical composition of traditionally used vegetable substrates in the
mushroom production industry (Table 2) shows that this raw material (grain waste) contains 12.5%
protein, 3.0% of fat; fiber -7.2% and therefore can be used for the cultivation of mushrooms.
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
4
Table 2. The chemical composition of grain waste and other vegetable substrates, % of dry weight
Substrate
Proteins
Lipids
Fibers
Ca
P
N
K
Grain waste
12,5
3,0
8,2
0,7
0,4
0,7
1,6
Burclover
, hay
14,8
22,8
28,9
1,5
0,2
2,4
2,0
Burclover
, straw
8,8
1,5
40,4
2,2
0,1
1,4
2,0
Barley, straw
3,7
1,6
37,7
0,3
0,11
0,6
1,3
Soy, straw
6,1
1,4
41,1
1,7
0,1
1,0
1,0
Soy, hay
14,1
2,4
27,2
1,3
0,2
2,4
0,8
Clover, hay
11,7
3,4
29,2
1,5
0,2
1,9
2,0
Corn stalk
2,3
0,4
32,1
0,2
0,02
0,4
0,4
Oats, straw
4,1
2,2
36,1
0,1
0,1
0,7
1,3
Wheat, straw
3,9
1,5
36,9
0,2
0,1
0,6
0,8
Sunflower husk
19,6
1,1
35,9
0,2
0,1
3,1
0,5
The rate of substrate coverage strongly depends on the seeding rate of oyster mushrooms. The higher
it is, the faster the biofouling of the substrate. The development of mycelium also depends on the quality
of the substrate, since competitive organisms inhibit and sometimes completely inhibit the growth of
mycelium. In the first week of incubation, the mycelium grows in thin threads covering the entire
substrate block- this is the stage of colonization. At the end of this stage, a small thickened cushion of
mycelium can already be seen around the perforations: the primordia mushrooms will be formed on this
roller in the future. During the second week of incubation, the nutrients of the substrate are being
consumed and the mycelium network starts developing and thickens - the block becomes whiter and
whiter, firmer to the touch. The best time to transfer the substrate blocks to the mushroom fruiting
workshop is when the whole substrate is covered by mycelium, but fungi in the form of stroma has not
yet formed a strong seal and the mushrooms from perforation did not appear yet. The dynamics of
mushroom biofouling of the substrate are presented in table 3.
Table 3. Dynamics of mushroom biofouling of the substrate
Substrate type
Date of
occurence
Inoculation Primordium
formation
1st
mushroom
harvest
2nd
mushroom
harvest
Control
-
wheat straw
2.12
15.12
21.12
28.12
Grain waste
2.12
19.12
23.12
29.12
Grain waste + birch sawdust
2.12
17.12
24.12
30.12
Birch Sawdust
2.12
18.12
24.12
30.12
Full biofouling of the substrate is determined visually. If necessary, cross-sections of the substrate
into units help determine the uniformity of the growth of mycelium in the thickness of the substrate. The
overexposure of blocks or reincubation cause either the appearance of stroma or the appearance of oyster
mushroom primordia.
In our study, the golden oyster mushroom showed a high colonization rate of the substrate. Primordia
began to form at 13-17 day. The first substrate completely colonized was the wheat straw substrate, and
the last was the grain waste substrate on day 17. A possible reason for this is a relative decrease in the
intensity of gas exchange in the volume of the starch-enriched substrate, which led to a slower formation
of primordia and later, of fruiting bodies and accordingly, an increase in the consumption of the substrate
to support the vital processes of the mycelium [22].
Oyster mushroom under high levels of carbon dioxide (as, for example, in the incubation chamber)
forms a larger number of fungal primordia than with an excess of fresh air. When overexposing
primordia for 1-2 days, deformed and damaged fruiting bodies appear.
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
5
The yield of the oyster mushroom Pleurotus citrinopileatus grown in laboratory conditions is
presented in Figure 1.
a)
b)
Figure 1.
Yield of golden oyster mushroom
Pleurotus citrinopileatus (a -
fruiting period, days; b
- yield referred to 1 kg of wet substrate,%; c -
yield
referred to 1 kg of wet substrate, g)
c)
According to the obtained data, the fruiting period of golden oyster mushrooms on the studied
substrates represented 26-28 days. This duration was more stretched on the variant auditioned of
sawdust. The maximum and the minimum yields were obtained on wheat straw substrate (171.2 g per
kg of substrate) and grain waste substrate (113.4 g per kg) respectively. On birch sawdust substrate and
on the substrate of grain waste and birch sawdust mixture, the yields reached 143.2 g and 130.3 g in this
order.
The most intense strain recovery was reached during the first wave of fruiting on grain waste and
wheat straw with 70.0 and 56.7% of the total yield, respectively. Such a high product recovery yield
obtained on the substrate of grain wastes is probably associated with a high content of available starch.
The product recovery was the lowest on the birch sawdust substrate (47.3%) due to its high cellulose
content. The mushroom yield in the first and second waves was approximately the same on the substrate
with on the substrate of grain waste and birch sawdust mixture (49.3 - 50.7%).
Under industrial conditions of oyster mushroom production, the most profitable is the two-week
harvest window, which shortens the production cycle duration and makes it possible to increase the
number of crop turns per year.
In the course of the experiment, the initial dry masses of all organic substrates were taken into
account; at the end, the mass of the fruiting bodies and the amount of undigested (residual) substrate
were taken into consideration (Fig. 2).
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
6
a)
b)
Figure 2.
Substrate conversion rates of Pleurotus
citrinopileatus mushroom (a: moisture content of
the initial substrate%; b: mushroom yield,%; c:
percentage of the substrate residue referred to its
initial amount,%)
c)
The largest amount of undigested substrate residue was obtained when using grain waste in its pure
form - 79.0%, which was related to a mushroom yield of 11.3%. When using grain wastes with the
addition of birch sawdust, the degree of digested substrate increased to 69.6%, and the mushroom yield
increased to 13.0%, which is lower than the control by 2.9 and 23.9% respectively.
In this way, it can be stated that increasing the nutritional value of the substrate by adding grain
processing waste results in a limited increase in the mushroom yield of Pleurotus citrinopileatus, since
at the same time, the gas exchange intensity decreases as well as the degree of substrate conversion.
Therefore, cellulose-containing components must be added to the substrate with grain waste. Thermal
or chemical treatments are also needed to suppress the development of microflora.
4. Conclusions
Grain wastes and grain processing wastes are harmless and easily amenable to enzymatic and
microbiological bioconversion. Golden oyster mushroom (Pleurotus citrinopileatus) grown under
laboratory condition on grain processing wastes demonstrated a high rate of substrate colonization. The
average yielding crop attained 113.4 g of fresh mushrooms grown on 1 kg of substrate under a relative
humidity of 70-75%. This promising work stream not only proposes a waste disposal method, but also,
a significant source of income for the grain processing enterprises.
References
[1] Kulikova E G, Efremova S Yu 2014 XXI vek: itogi proshlogo i problemy nastoyashchego plyus
1(17) pp 103-9
[2] Kulikova E G 2013 Innovacionnye tekhnologii v APK: teoriya i praktika. Sbornik statej
Vserossijskoj nauchno-prakticheskoj konferencii pp 110-3
[3] Neverova O A, Gorelikova G A, Poznyakovskij V M Pishchevaya biotekhnologiya produktov iz
Efficient waste treatment-2018
IOP Conf. Series: Earth and Environmental Science 337 (2019) 012033
IOP Publishing
doi:10.1088/1755-1315/337/1/012033
7
syr'ya rastitel'nogo proiskhozhdeniya, Novosibirsk p 416
[4] SHapavalov L V 1988 Zernovye kul'tury 2 pp 23-4
[5] Kulikova E G, Logvina O A 2015 Vliyanie spichechnogo proizvodstva na sostoyanie ehkosistem
i biokonversiya ego othodov veshenkoj limonnoshlyapkovoj, XXI vek: itogi proshlogo i
problemy nastoyashchego plyus 5(27) pp 32-9
[6] Zubareva I M, Lyapustіna O V, Lebedeva O M, Smetanіn V T 2010 Nedelya ecologa tezisy
dokladov Mezhdunarodnogo nauchnogo simpoziuma pp 78-81
[7] Sobgaida N A, Olshanskaja L N, Makarova Y A 2009 Khim. Neftegaz. Mashinstr 9 pp 36-9
[8] Gambato G, Todescato K, Pavao E, Scortegagna A, Fontana R, Salvador M, Camassola M 2016
Bioresource Technology 207 pp 46-51
[9] Owaid M, Abed I, Al-Saeedi P 2015 Emirates Journal of Food and Agriculture 27(7) pp 556-61
[10] Jeyanthi Rebecca L, Seshiah C, Kowsalya E, Sharmila P 2015 International Journal of Pharmacy
and Technology 7(2) pp 8887-88
[11] Sharmila P, Jeyanthi Rebecca L, Tissopi T, Kowsalya E 2015 Der Pharmacia Lettre 7(8) pp 193-
6
[12] Gambato G, Todescato K, Pavao M, Salvador M, Camassola M 2016 Bioresource Technology
207 pp 46-51
[13] Owaid M N, Abed A M, Nassar B M 2015 Emirates Journal of Food and Agriculture 27(7) pp.
537-41
[14] Dawidowicz L, Jasinska A, Siwulski M 2018 Notulae Botanicae Horti Agrobotanici Cluj-Napoca
46(1) pp 156-60
[15] Bis'ko N A Biologiya i kul'tivirovanie s"edobnyh gribov roda veshenka1987 p 148
[16] Dudka I A, Vasser S P Griby: Spravochnik mikologa i gribnika1987 p 535
[17] Morozov A I Griby: Rukovodstvo k razvedeniyu 2000 p 304
[18] Perstieva E V, Dreveckaya V L Vyrashchivanie gribov roda Pleurotus na tverdyh othodah//
EHkologicheskie problemy biodegeneracii promylennyh, storoitel'nyh materialov i othodov
proizvodstv: mat. vseros. konf. - Penza, 1998 pp 97-98.
[19] Kiseleva O V Tekhnologiya vyrashchivaniya biomassy miceliya serno-zheltogo trutovika
Laetiporus sulphureus v usloviyah glubinnogo kul'tivirovaniya s cel'yu polucheniya belkovyh
pishchevyh dobavok // avtoref dis…kand tekhn. Nauk. – Krasnoyarsk 2013 p 20
[20] Ternova K G Agrotekhnologicheskoe obosnovanie kul'tivirovaniya veshenki obyknovennoj na
kostre l'na // avtoref dis…kand s.-h. nauk. – Moskva 2006 p 20
[21] Sazonova I A 2012 Ecologicheskaya biotekhnologiya p 106
[22] Manukovskij N S Kinetika biokonversii lignocellyuloz 1990 p 112
