The search for efficient oleaginous microorganisms, which can be an alternative to fossil fuels and biofuels obtained from oilseed crops, has been going on for many years. The suitability of microorganisms in this regard is determined by their ability to biosynthesize lipids with preferred fatty acid profile along with the concurrent utilization of energy-rich industrial waste. In this study, we isolated, characterized, and identified kefir yeast strains using molecular biology techniques. The yeast isolates identified were
Oleaginous yeasts are capable of accumulating over 20% of their cell mass as intracellular lipids and the production of microbiological lipids is defined as SCO (single cell oil) [
In developed countries, the problem of waste utilization, which is one of the most important priorities, needs to be addressed. Starch processing plants are arduous manufacturers of sewage. The production of potato starch involves formation of three types of organic wastes: potato juice, wastewater, and pulp. Potato wastewater is 10-fold diluted potato juice created during starch milk refining. To reduce the burden on potato wastewater, the starch processing plants perform the process of deproteinization by applying thermal-acid coagulation to remove proteins, which is then used in the production of animal feed [
Deproteinated potato wastewater (DPW) can act as a growth medium for yeast [
An inconvenient waste of the food industry is whey, which is generated in large quantities by the dairy industry. The possibility of biotechnological management of whey is largely dependent on the abilities of its microorganisms in assimilating or fermenting milk sugar—lactose. Kefir may be the natural environment for the yeast that have the ability to assimilate lactose. Therefore, it can be a source of lactose-positive yeast strains.
Kefir is a fermented milk product manufactured from milk subjected to lactic acid-alcohol fermentation in the presence of kefir grains. Kefir grains have a characteristic microflora that includes lactic acid-fermenting bacteria, acetic acid bacteria, and yeasts [
The aim of this investigation was to isolate yeast strains from kefir and to study their biochemical behavior emphasizing their ability to accumulate lipids. The newly isolated strains were identified according to their internal transcribed spacer (ITS) sequence similarities. The studies regarding lipid accumulation abilities and fatty acid composition were performed. The concept of the utilization of potato wastewater as a source of assimilable nitrogen and other essential elements for oleaginous kefir yeast breeding was examined.
Natural kefirs were purchased from Polish manufacturers. All products were examined within their shelf life period. Kefir sample (10 g) was aseptically withdrawn and suspended in 90 mL of physiological saline. One mL culture from this dilution was loaded on Sabouraud dextrose agar with chloramphenicol and incubated at 28°C for 72 h. After incubation, the culture was evaluated for bacterial growth, and yeast colonies from the agar plate were transferred using streaking technique on Sabouraud dextrose agar and incubated at 28°C again for 72 h. It was then inoculated by streaking on YPD medium (composed of glucose 20 g L−1, peptone 20 g L−1, yeast extract 10 g L−1, and agar 20 g L−1, pH 5.5). The so-obtained strains were stored on YPD agar medium with pH 5.6 at 6°C, restreaking again on fresh medium every 3-4 weeks.
The yeast strains were identified using Api 20 AUX tests [BioMerieux, France] according to the manufacturer’s instructions. Prior to testing, the isolates were subcultured on to Sabouraud dextrose agar and were incubated at 28°C in an aerobic atmosphere for 24–48 h.
After 24 h culture in YPD medium, yeast biomass (2 cm3) was centrifuged at 716 ×g and 4°C for 10 min. Then, it was rinsed twice with sterile deionized water and suspended in 300
DNA was amplified according to a previously described procedure [
Two restriction enzymes, namely,
Amplicons were sequenced using Genomed, Warsaw, Poland. DNA sequences were analyzed with basic local alignment search tool (BLAST). Phylogenetic analysis was performed using MEGA 7 by applying neighbor-joining algorithm [
The yeast strains were cultured using the following control media: (a) YPGlc containing 20 g L−1 peptone, 10 g L−1 yeast extract, and 50 g L−1 glucose; (b) YPLac containing 20 g L−1 peptone, 10 g L−1 yeast extract, and 50 g L−1 lactose; and (c) YPGly containing 20 g L−1 peptone, 10 g L−1 yeast extract, and 50 g L−1 glycerol (pH 5.6). All media were sterilized in an autoclave for 20 min at 121°C.
Potato wastewater was obtained from the processing Line of PEPEES SA Company (Łomża, Poland) during the potato campaign in autumn 2015, after coagulating the proteins using thermal-acid coagulation technique. The wastewater was sterilized for further evaluation (121°C/0.1 MPa/20 min) (HiCLAVE HG-80 autoclave, HMC Europe), as we had detected the presence of aerobic spore bacilli, mold, and yeast spores. DPW was centrifuged to remove precipitates formed during sterilization (3200 ×g/20 min) (Eppendorf 5810 Centrifuge), which was followed by the addition of glucose (50 g L−1), lactose (50 g L−1), or glycerol (50 g L−1). The pH was adjusted to 5.6 using 0.1 M NaOH and the entire mixture was sterilized according to the procedure described above. The experimental media supplemented with glucose, lactose, and glycerol will be, respectively, referred to as DPWGlc, DPWLac, and DPWGly in future of this manuscript.
Fifty-milliliter liquid YPD medium was inoculated with the selected strain from the slant cultures in round flat-bottom flask. The cultures were grown at 28°C (MaxQ 4000, Barnstead) for 24 h on a reciprocating shaker with a frequency of 200 cycles/min. The inoculum obtained by this method constituted material for inoculation of microculture in Bioscreen C system and for proper culture experiments.
Growth of strains was analyzed in the experimental media using Bioscreen C apparatus (Oy Growth Curves Ab Ltd., Finland). Briefly, 270
All cultures were grown in 500 mL flasks. Media (90 mL) were inoculated with inoculum constituting 10% of the culture volume. The cultures were incubated for 96 h at 28°C on SM-30 Control (Buehler, Germany) shaker at a frequency of 200 cycles min−1. Each culture variant was grown in triplicate.
The examination of the shape and size of the cells was conducted using the microscope (Opta-Tech 300, Poland) and microscopic camera (Opta-Tech) integrated OptaWiew7 (V:2.1.) software. The length (longer dimension), width (shorter dimension), and surface of minimum of 100 cells were measured.
OD of culture was determined after centrifugation of 2 mL of culture (1610 ×g/5 min) (Eppendorf mini Spin plus). The supernatant was decanted, and the biomass precipitate was suspended in 2 mL of distilled water. OD was measured spectrophotometrically at a wavelength of 600 nm against distilled water as blank (UV – 1800 UV/VIS, RayLeigh Analytical Instrument).
To determine the biomass yield after completion of incubation, postculture fluid was transferred to a dried and weighed extraction thimble and centrifuged (2000 ×g/20 min) (Eppendorf Centrifuge 5804R). Then, the supernatant was decanted and the precipitate containing the biomass was washed twice with sterile distilled water followed by drying until a constant weight was achieved at 105°C (SML 32/250 Zelmed drier, Poland). Biomass yield was expressed in terms of grams of dry yeast per liter of culture medium (g d.w. L−1 medium). The biomass concentration at the beginning of culture was about 0.4 g d.w. L−1 medium for each strain.
After culturing, yeast biomass was centrifuged (2000 ×g/4°C/10 min) (Eppendorf Centrifuge 5804R). Then, it was rinsed twice with sterile deionized water and then dried at 80°C until a constant weight was achieved. The biomass yield was expressed in terms of grams dry yeast per liter of the culture medium (g d.w. L−1 medium). The lipid content in yeast biomass was determined according to the method of Bligh and Dyer and modified based on Zhang et al. [
The dry matter content in DPW was determined by gravimetric method (105°C, 24 h, SML 32/250, Zetmet). The nitrogen content was determined by the Kjeldahl method (Büchi Digestion Unit K-435, Büchi Distillation Unit K-355) [
Proteins were separated on a polyacrylamide gel electrophoresis under denaturing conditions (SDS-PAGE) using 3% thickening silica gel and 12% separating gel. Protein was denatured in a temperature range of 90–100°C for 5 min with concurrent shaking (Eppendorf Thermomixer Comfort, Germany). Then, electrophoresis was performed using a Mini Protean® 3 Bio-Rad device at constant current of 20 mA (voltage is 200 V) in 1x Tris-glycine buffer with a pH of 8.3. An appropriate molecular weight marker (Precision Plus Protein Dual Xtra Standards, Bio-Rad) was used to determine the mass of protein fractions. For visualization, the gel was stained with Coomassie Brilliant Blue R-250. Electrophoretically separated proteins were documented using a gel recording system (GelDoc 2000, Bio-Rad, France). Proteins were analyzed using the Quantity One version 4.2.1 (France) computer program [
All values are mean of three separate experiments. The results obtained were statistically analyzed using the STATISTICA V.10 program (StatSoft Polska Sp. z o.o., Krakow, Poland). Analysis of variance (ANOVA) was performed using Tukey’s test at
The properties of fatty acids methyl-esters, namely, unsaturation degree (UN), cetane number (CN), length of chain (LC), low caloric value (LCV), flash point (FP), and viscosity ( (see [ (see [ (see [
where
In this study, the degree of identification of yeast isolates based on API 20 AUX system was high, which was found to be more than 99%. This allowed the identification of seven strains from the isolates. The species identified were as follows:
Results of an identification of kefir yeast isolates using API 20 AUX and genetic analysis.
API name isolate identification | Origin | bp | Name of isolate |
---|---|---|---|
|
1 caaaaaacaa aactttcaac aacggatctc ttggttctcg catcgatgaa gagcgcagcg |
326 |
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1 acttttgctt tggtctggac tagaaatagt ttgggccaga ggtttactga actaaacttc |
394 |
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1 gaacttttgc tttggtctgg actagaaata gtttgggcca gaggtttact gaactaaact |
443 |
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1 cttttgcttt ggtctggact agaaatagtt tgggccagag gtttactgaa ctaaacttca |
426 |
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1 gccgaaccag cgcttaattg cgcggtttgg tgggtctctg tagctcagta gcactattac |
338 |
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1 ttctcatcct aaacacaatg gagttttttc tctatgaact acttccctgg agagctcgtc |
401 |
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1 ctgacacata cacacagtgg agatatattc tttcttcttc ttcttctttg ggggacggcg |
484 |
|
API: Api 20 AUX tests; bp: base pairs.
Summary of sizes in base pairs of the PCR products and the restriction fragments of yeast DNA.
Strain | PCR-amplified product (bp) | Restriction fragments (bp) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
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| ||||||||||
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460 | 290 | 90 | 80 | 360 | 100 | |||||
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640 | 410 | 140 | 90 | 450 | 190 | |||||
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640 | 410 | 140 | 90 | 450 | 190 | |||||
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640 | 410 | 140 | 90 | 450 | 190 | |||||
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690 | 550 | 130 | 510 | 110 | 70 | |||||
|
700 | 620 | 80 | 630 | 70 | ||||||
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600 | 600 | 520 | 80 |
bp: base pairs; PCR: polymerase chain reaction.
(a) Electrophoretic separation of PCR amplification products on 2% agarose gel (M—molecular marker; 1—
We found, after electrophoretic separation of the PCR products as a result of obtaining of determined length of amplicons and the use of restriction enzyme H
All isolated yeast strains formed colonies of white to various shadows of cream and beige color on the solid medium and were mostly characterized by shape specific for yeasts. Strains
The lowest dimensions in YPD medium (Table S1) were characteristic for the cells of both
The physicochemical parameters of wastewater obtained from the process line after deproteinization stage shows Table
Composition of deproteinated potato wastewater used in this study.
Parameter | Unit | Deproteinated potato wastewater |
---|---|---|
pH | 4.9 |
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Dry substance | g d.w. 100 cm−3 | 3.3260 |
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Directly reducing sugars | g 100 cm−3 | 0.4400 |
Nitrogen | 0.1620 |
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Potassium | 0.4137 |
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Phosphorus | 0.0333 |
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Magnesium | 0.0236 |
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Calcium | 0.0100 |
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Sodium | mg 100 cm−3 | 6.063 |
Manganese | 0.181 |
Isolated yeast strains were able to assimilate the examined carbon sources. The cells grew the fastest in the glucose-supplemented media with peptone and yeast extract. The use of lactose and glycerol significantly reduced the specific growth rate (Table S2). We observed that the growth of the yeast isolates in media with wastewater was characterized by an extended lag-phase (data not shown) and lower specific growth rate compared to the control YP medium. Supplementation of lactose and glycerol in these media reduced the specific growth rate compared to glucose. Only in case of
The highest biomass yield (in the range of 13.5–14.8 g L−1) was observed in the YPGlc medium in case of three strains of
Parameters characterizing the growth and lipid production of kefir yeast strains in media supplemented with glucose, lactose, and glycerol.
Strain | Biomass |
|
Lipids |
|
pH | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Glc | Lac | Gly | Glc | Lac | Gly | Glc | Lac | Gly | Glc | Lac | Gly | Glc | Lac | Gly | |
g L−1 | g L−1 h−1 | g L−1 | g L−1 h−1 | ||||||||||||
YP medium | |||||||||||||||
|
12.2 |
13.5 |
9.8 |
0.127 | 0.141 | 0.102 | 4.04 |
3.38 |
1.71 |
0.042 | 0.035 | 0.018 | 5.10 | 5.17 | 5.62 |
|
13.5 |
12.9 |
11.8 |
0.140 | 0.134 | 0.123 | 6.31 |
2.02 |
2.26 |
0.066 | 0.021 | 0.024 | 7.31 | 7.58 | 6.01 |
|
13.8 |
13.0 |
13.6 |
0.144 | 0.135 | 0.142 | 1.14 |
1.77 |
3.28 |
0.012 | 0.018 | 0.034 | 6.69 | 6.97 | 7.46 |
|
14.8 |
10.7 |
10.2 |
0.154 | 0.111 | 0.106 | 5.65 |
1.78 |
1.85 |
0.059 | 0.018 | 0.019 | 7.23 | 7.69 | 7.63 |
|
11.0 |
10.4 |
12.1 |
0.114 | 0.108 | 0.126 | 1.70 |
1.32 |
0.87 |
0.018 | 0.014 | 0.009 | 4.29 | 5.19 | 6.30 |
|
12.9 |
12.2 |
10.7 |
0.134 | 0.127 | 0.111 | 3.71 |
4.76 |
0.50 |
0.039 | 0.049 | 0.005 | 7.31 | 7.09 | 7.03 |
|
13.7 |
12.4 |
11.3 |
0.143 | 0.129 | 0.118 | 4.44 |
1.97 |
2.34 |
0.046 | 0.020 | 0.024 | 5.79 | 6.31 | 5.04 |
|
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DPW medium | |||||||||||||||
|
10.5 |
10.9 |
10.9 |
0.109 | 0.113 | 0.113 | 0.36 |
1.58 |
2.35 |
0.004 | 0.016 | 0.024 | 8.51 | 8.00 | 8.01 |
|
12.3 |
11.6 |
11.0 |
0.128 | 0.121 | 0.112 | 1.12 |
1.99 |
1.79 |
0.012 | 0.021 | 0.018 | 7.56 | 7.93 | 8.44 |
|
11.7 |
12.4 |
10.8 |
0.122 | 0.129 | 0.112 | 0.85 |
0.69 |
1.92 |
0.009 | 0.007 | 0.020 | 7.30 | 8.43 | 8.63 |
|
11.4 |
11.7 |
10.5 |
0.119 | 0.122 | 0.111 | 2.80 |
2.43 |
2.21 |
0.030 | 0.025 | 0.023 | 7.10 | 8.09 | 8.57 |
|
9.9 |
11.6 |
10.3 |
0.103 | 0.121 | 0.107 | 0.79 |
1.91 |
2.22 |
0.008 | 0.019 | 0.023 | 8.13 | 8.00 | 8.01 |
|
10.3 |
11.4 |
10.7 |
0.108 | 0.119 | 0.111 | 3.56 |
1.74 |
2.16 |
0.037 | 0.018 | 0.022 | 7.94 | 8.52 | 8.42 |
|
10.1 |
11.9 |
11.1 |
0.105 | 0.123 | 0.115 | 0.52 |
0.85 |
1.97 |
0.005 | 0.009 | 0.020 | 7.13 | 8.13 | 8.28 |
The final concentration of biomass, the volumetric productivities of biomass (
The highest lipid content after incubation in YP media with glucose was found in the biomass of
Total lipid production (% cell dry waste (CDW)) in kefir yeast biomass after culturing in YP media supplemented with glucose, lactose, and glycerol.
Lipid content in dry biomass after the culturing in DPWGly medium exceeded 20% for
Effect of culture time on lipid content, expressed as % cell dry waste (CDW): dark-colored bars cell dry waste—72 h and light-colored bars—96 h, in deproteinated potato wastewater (DPW) media with glucose, lactose, and glycerol.
The use of DPW medium and glucose as carbon source revealed major differences in the ability of the examined strains for lipids biosynthesis. The share of this component higher than 20% g−1 d.w. biomass was only noted for
Based on these findings, we can conclude that lipid content in d.w. of the examined yeast biomass was dependent on the duration of the culture, and, in all variants of the examined media, the share of this intracellular component increased after 72 h (Figure
The initial pH of all media was 5.6. Cultures of examined yeast strains in all variants of media, experimental and control, caused significant changes in pH (Table
The results of fatty acid profile after culturing yeast isolates in control (YPD) media supplemented with glucose are presented in Table
Relative fatty acid composition (%) in kefir yeast biomass after culturing in medium supplemented with glucose (YPD medium).
Strain | Relative fatty acids composition (%) | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
C12:0 | C14:0 | C16:0 | C16:1 | C17:1 | C18:0 | C18:1 | C18:2 | C18:3 |
C20:1 |
C20:3 |
C20:4 |
C22:2 | C22:4 | C24:0 | |
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n.d. | n.d. |
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n.d. |
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n.d. | n.d. | n.d. | n.d. | n.d. | n.d. |
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n.d. | n.d. |
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n.d. |
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n.d. | n.d. | n.d. |
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n.d. |
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n.d. |
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n.d. |
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n.d. | n.d. | n.d. |
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n.d. | n.d. |
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n.d. |
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n.d. |
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n.d. | n.d. | n.d. | n.d. |
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n.d. |
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n.d. |
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n.d. |
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n.d. |
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n.d. |
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n.d. | n.d. |
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n.d. |
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n.d. |
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n.d. | n.d. |
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n.d. |
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n.d. | n.d. |
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n.d. |
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n.d. = not detected. a, b, c mean values marked with the same letters do not differ significantly. Tukey’s test
Total content of particular groups of fatty acids after culturing in all media supplemented with glucose, lactose, and glycerol on an example of
The largest share of PUFA after culturing in experimental media with wastewater and glucose was found in the biomass of the three strains belonging to
The molecular studies aimed at identification of general yeast species have emphasized either coding, that is, D1/D2 variable domains of a large subunit rDNA, or noncoding, that is, ITS regions of the DNA [
The wrong identification of
Most of the identified strains in studies discussed herein were previously isolated from kefir or kefir grains by other authors (Table
Yeast strains isolated from kefir and kefir grains: a literature review.
Strain | References |
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All examined yeast strains were able to assimilate glucose, glycerol, and lactose. According to the CBS-KNAW Collections data, the
The study on wastewater composition confirmed that it can be a valuable source of nitrogen, potassium, phosphorus, and other elements in yeast cultures. High percentage of potassium especially in the wastewater results from the characteristics of the raw material—potatoes, which are a rich source of this element. However, it should be taken into account that the chemical composition of this waste depends on many factors, which include, inter alia, potato variety, type of soil and fertilization, and the technology and the efficiency of obtaining starch and deproteinization. Compared to the waste originating from a different region, the wastewater used in this study was characterized by threefold lower share of calcium and lower concentration of protein compounds [
The available nitrogen forms in wastewater are proteins, amino acids, purines, and pyrimidines. The easy soluble protein fractions get into a potato wastewater containing 2–5% of solids, of which crude protein represents about 35% [
Intracellular lipid content was dependent on the strain and the applied medium. It is assumed that the process of fat accumulation is induced by a C : N ratio of greater than 20, and in the case of some microorganisms it may be higher than 70 [
Until now, pure glycerol being used as sole carbon source supported the growth and lipid accumulation of
Studies regarding the use of lactose as carbon source during the culture of oleaginous microorganisms are very scarce. To date, only one study related to the effect of lactose on the growth and accumulation of fats by fungi of
Our results confirm the well-known theory of efficient lipid synthesis in the late stationary phase and at the same time suggest the need to optimize the culture time. We found a large increase in biomass yield and fat content between third and fourth day in the media with lactose, which suggests that lactose is assimilated in a slow manner compared to other carbon sources, which resulted in the biosynthesis of fats observed on fourth day.
The optimal pH value of the culture medium with respect to promoting lipid biosynthesis by the yeast is in the range of 4–8, depending on the type of microorganism and the used carbon source [
Yeast growth is more effective when the pH of the medium is slightly acidic, and, therefore, alkalization of the environment may be a stress factor for the cell. A strong alkalization of the environment during yeast culture in DPW disturbs the homeostasis of nutrients and affects an expression of genes of glucose uptake and metabolism. The high pH causes a temporary drop in the concentration of cAMP and inhibition of protein kinase activator (PKA, protein kinase A). Consequently, the transcription factor Msn2/4p is subject to a rapid activation in the nucleus and activates gene related to stress, related, inter alia, to trehalose synthesis [
According to the data described in the literature, the temperature of yeast culture aimed at increasing fats biosynthesis should be 25–30°C. It affects the proliferation rate of the yeast cells and fatty acid composition [
Fats synthesized by oleaginous yeast primarily contain the following fatty acids: myristic (C14:0), palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and linolenic acid (C18:3) [
The possibility of using fat as a raw material in the production of biodiesel depends on the different physicochemical characteristics of the fuel. The transesterification of microbial oils with a methanol yields to the corresponding monoalkyl esters so the chemical structure of the fatty acids methyl esters influences fuel properties. The successful commercialization of vegetable oils as biodiesel sources has been accompanied by the development of international standards. Some biodiesel standards are European standard EN 14124 and American Society for Testing and Materials ASTM D6751. In our study biodiesel properties were determined using mathematical equations based on the fatty acids compositions. An industrially used biodiesel is primarily composed of palmitic, stearic, oleic, linoleic, and linolenic acids. Biofuels used in Europe are characterized by certain specification, according to which the content of linolenic ester acid should not exceed 12% and the methyl esters of polyunsaturated fatty acids (containing, inter alia, four double bonds)—1% [
The fatty acid composition characteristic for the examined kefir yeast isolates is therefore appropriate in relation to the European Union (EU) requirements for biofuels, and, therefore, they can be a source of SCO. They contain C16:0, C18:0, and C18:2 acids, in particular C18:1. Fats from all strains contained no more than 2.6% of linolenic acid (C18:3 n-3). The suitable selection of carbon source during culture can reduce the amount of PUFA with more than four double bonds. Biodiesel properties based on the fatty acids composition of the microbial oil producers by kefir yeast strain isolates in different media are shown in Table
Biodiesel properties based on the fatty acids composition of the microbial oil producers by kefir yeast strain isolates in different media.
Strain | Carbon source | Nitrogen source | UD | CN | LC | LCV |
FP |
|
---|---|---|---|---|---|---|---|---|
|
Glucose | Peptone | 0,94 | 58 | 17,61 | 35595,71 | 172,41 | 5,32 |
DPW | 1,04 | 53 | 17,65 | 37575,43 | 170,98 | 5,19 | ||
Lactose | Peptone | 0,77 | 61 | 17,40 | 37560,82 | 170,06 | 5,45 | |
DPW | 1,00 | 54 | 17,68 | 37604,87 | 173,07 | 5,27 | ||
Glycerol | Peptone | 0,84 | 59 | 17,49 | 37573,25 | 170,86 | 5,39 | |
DPW | 1,03 | 54 | 17,69 | 37598,66 | 172,62 | 5,24 | ||
|
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|
Glucose | Peptone | 0,88 | 55 | 18,01 | 37813,79 | 189,27 | 5,67 |
DPW | 0,99 | 56 | 17,61 | 37576,05 | 170,99 | 5,25 | ||
Lactose | Peptone | 0,65 | 65 | 17,45 | 37630,43 | 175,44 | 5,68 | |
DPW | 0,70 | 59 | 17,19 | 37474,17 | 164,08 | 5,38 | ||
Glycerol | Peptone | 0,74 | 58 | 17,44 | 37587,95 | 172,06 | 5,52 | |
DPW | 0,91 | 56 | 17,61 | 37559,11 | 169,86 | 5,18 | ||
|
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Glucose | Peptone | 0,75 | 53 | 17,31 | 37522,23 | 167,36 | 5,41 |
DPW | 0,88 | 55 | 17,49 | 37559,45 | 169,84 | 5,33 | ||
Lactose | Peptone | 0,86 | 51 | 18,21 | 37917,75 | 198,08 | 5,84 | |
DPW | 0,92 | 57 | 17,51 | 37553,68 | 169,41 | 5,28 | ||
Glycerol | Peptone | 0,75 | 57 | 17,24 | 37488,15 | 165,00 | 5,37 | |
DPW | 0,92 | 59 | 17,41 | 37504,99 | 166,04 | 5,23 | ||
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Glucose | Peptone | 0,80 | 58 | 17,89 | 37782,18 | 186,87 | 5,72 |
DPW | 0,92 | 58 | 17,58 | 37585,46 | 171,68 | 5,33 | ||
Lactose | Peptone | 0,86 | 51 | 15,53 | 37585,35 | 171,71 | 5,39 | |
DPW | 0,92 | 57 | 17,47 | 37535,54 | 168,15 | 5,26 | ||
Glycerol | Peptone | 0,75 | 40 | 16,19 | 36976,93 | 135,68 | 4,69 | |
DPW | 0,92 | 58 | 17,32 | 37461,17 | 163,09 | 5,16 | ||
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Glucose | Peptone | 0,70 | 41 | 17,85 | 37804,41 | 188,96 | 5,86 |
DPW | 0,85 | 57 | 16,55 | 37118,81 | 142,77 | 4,79 | ||
Lactose | Peptone | 0,77 | 59 | 17,34 | 37531,19 | 167,96 | 5,41 | |
DPW | 1,05 | 52 | 17,00 | 37256,05 | 150,61 | 4,79 | ||
Glycerol | Peptone | 0,90 | 56 | 17,02 | 37323,10 | 154,32 | 5,00 | |
DPW | 1,06 | 51 | 16,99 | 37100,16 | 142,32 | 4,59 | ||
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Glucose | Peptone | 0,75 | 45 | 18,19 | 37951,52 | 201,39 | 6,02 |
DPW | 0,89 | 56 | 17,35 | 37488,00 | 164,89 | 5,23 | ||
Lactose | Peptone | 0,76 | 46 | 18,11 | 37907,84 | 197,52 | 5,94 | |
DPW | 0,85 | 59 | 17,25 | 37453,83 | 162,61 | 5,23 | ||
Glycerol | Peptone | 0,85 | 59 | 17,43 | 37542,21 | 168,65 | 5,34 | |
DPW | 0,91 | 57 | 17,51 | 37557,56 | 169,69 | 5,30 | ||
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Glucose | Peptone | 0,82 | 54 | 17,85 | 37754,23 | 184,57 | 5,66 |
DPW | 0,85 | 59 | 17,45 | 37554,12 | 169,49 | 5,36 | ||
Lactose | Peptone | 0,67 | 55 | 16,12 | 36979,07 | 135,56 | 4,76 | |
DPW | 0,81 | 61 | 17,38 | 37535,33 | 168,20 | 5,37 | ||
Glycerol | Peptone | 0,86 | 58 | 17,50 | 37570,52 | 170,64 | 5,36 | |
DPW | 0,91 | 64 | 17,55 | 37577,03 | 171,08 | 5,33 |
Unsaturation degree (UN), cetane number (CN), length of chain (LC), low caloric value (LCV), flash point (FP), and viscosity (
In conclusion, the isolated kefir yeast strains have demonstrated their ability to biosynthesize intracellular lipids with a concurrent utilization of deproteinated wastewater in this study. Regardless of the carbon source, the use of deproteinated potato wastewater promoted palmitoleic acid biosynthesis by
This article does not contain any studies with human participants or animals performed by any of the authors.
The authors declare that they have no conflicts of interest.
The authors would like to acknowledge Maria Stańkowska at PEPEES S.A. in Łomża (Poland, Mazovia Voivode) for deproteinated water juice.