INTRODUCTION:

Global energy demand and consumption are continuously increasing with the rapidly growing world population. This has resulted in a grave depletion of fossil-fuel reservoirs and The exploitation of fossil fuels is responsible for 73% of global carbon dioxide emissions which are considered to be the main factor contributing to global warming and environmental change¹^,². Therefore, there has been an emergent need for alternative renewable fuel sources to replace fossil fuel based conventional energy sources³.

These biomasses are a renewable, abundantly available, and low-cost feedstock on the renewable energy technology platform providing a great potential for production biofuels of second-generation¹. Bio-fuels are attracting growing interest around the world, with some governments announcing commitments to bio-fuel programs as a way to both reduce greenhouse gas emissions and dependence on petroleum-based fuels. Bioethanol is by far the most widely used bio-fuel for transportation worldwide, because it is a renew- able, biodegradable resource, nontoxic, and it is oxygenated, thereby provides the potential to reduce particulate emissions in engines⁴^,⁵. Among them, Bioethanol is nowadays increasingly used as ecofriendly is one of the most important biofuels generated from renewable resources such as corn mostly in the USA and sugarcane in Brazil as well as carob⁶ . Bioethanol is ethanol extracted by fermentation, fermentation is anaerobic bioconversion in the presence of yeast and in appropriate conditions of temperature and pH, the fermentation of sugars contained in the biomass⁷. vegetable biomass as feedstock for bioethanol production allows for recycling the CO2 released during combustion, reducing the CO2 emissions⁵. Nowadays, the commercial bioethanol is almost entirely of ﬁrst generation since food crops are used as feedstock: sugarcane in Brazil, corn in the US, and wheat and sugar beet in the European Union (EU), rice straw⁸, tea processing waste⁹^,¹⁰, rice hull¹¹^,¹² , barley husk, wheat bran, rye bran¹³, Ulva lactuca¹⁴, and taro waste¹⁵, and the production of ethanol is increasing every day¹⁶. The main disadvantage of ﬁrst generation bioethanol is the competition over the utilization of arable land for cultivation of food crops between biofuel feedstocks, thus resulting on the increase of food prices⁵^,¹⁷. In the present study is valorization of biomass is made possible for any product with low market value obtaining bioethanol which constitutes a product of high added value, and that from the bio-valuation of poor-quality dates called we chose " Degla Bayda " since is a poor quality in Algeria.

MATERIALS AND METHODS:

Collection of samples:

Dates (Degla Bayda) was collected from Mr. Babziz farm in the region of Ouargla in Algeria which is characterized by the production of a large quantity of dates. The collected dates were manually cleaned were cleaned by tap water and pitted. Afterward, the samples later and were cut into small pieces and served as a working sample for the experiment. A yeast commercial Saccharomyces cerevisiae were used for fermentation.

Extraction of date juice:

The juice is a sweet liquid that is prepared, the date is obtained by maceration of dates pitted in hot water for 5 hours. The quantity is determined by 400 g of date on each 1L of distilled water. Finally, the solution is filtered to separate the musts and dates, we get 400 ml of date juice¹⁸.

Bioethanol fermentation:

Ethanol fermentation was carried out using 100 ml of date juice which the best hydrolysis treatment based on the number of sugars produced from date. Yeast is used S. cerevisiae in the fermentation process by different the amount at under various conditions of pH and temperature and time for the best yield of bioethanol production¹⁸^,¹⁹.

Distillation and rectification:

At the end of the fermentation, a date wine is obtained which must be filtered to separate the yeast. Fractional distillation is a process used to separate ethanol from water according to their different volatilities. This process essentially consists of boiling the ethanol-water mixture. It is distilled at a temperature of about 80 °C and 78 ° C³^,⁷.

Bioethanol Yield:

We calculated the yield of bioethanol extracted using the following relation:

R=(Quantity of Alcohol (v))/(Quantity of Date (w))×100

Bioethanol characteristics:

In order to see if our extracted bioethanol complies with international standards, we have analyses physic-chemical parameters for our bioethanol, the parameters we used are: Physical state, color, pH, density, Boiling Point²⁰^,²¹.

IR spectrometry:

The FT-IR spectra were recorded using Agilent Resolution Pro spectrometer at ambient temperature in the wave number 400-4000 cm^-1.

RESULTS AND DISCUSSION:

Bioethanol Yield:

The effects of pH, temperature, time, and ratio of yeast on the ethanol yield, substrate consumption and product formation rates were analyzed in fermentation²². Figure 1,2,3, and 4 show the experimental results for the fermentation.

Effect of pH on Bioethanol Yield:

The effect of pH on ethanol fermentation was studied at different pH ranging from pH 4.0 to 6.0 for used yeast strain namely commercial S. cerevisiae, incubation was carried out at 32°C, for 24 hours of fermentation period. Glucose conversion was continuing simultaneously during the fermentation. As shown in (Fig.1) the yield of ethanol was increased between pH 4.0 to 5.0 and then decreased below this value. The maximum of yield ethanol 36.25 % at pH 5.0.

Figure.1: Effect of pH on Bioethanol Yield

Effect of Temperature on Bioethanol Yield:

Bioethanol production affected by the temperature variation. Under suggested fermentation protocol, commercial S. cerevisiae Yeast strain showed diverse results under different temperature conditions (28℃, 30℃, 32℃, 34℃, 36°C) with regarding to bioethanol production (Fig.2). The best bioethanol yield was reported 36.25 % at 32 ℃, while at 30℃ and 34°C, bioethanol productions were 18.25% and 23.75 % On the order, a reduction in ethanol production was occurred at 28°C and 36°C was by 15.5%, 17.5% On the order. These results may be due to the reduction in the growth of S. cerevisiae yeast at higher and very low temperature that too decreased the rate of fermentation process.

Figure.2: Effect of Temperature on Bioethanol Yield

Effect of the amount of yeast on bioethanol yield:

The effect of the amount of yeast on bioethanol yield in different amounts was investigated 0.25, 0.50, 1.0, 1.25, 1.5, 2.0g by other fermentation conditions constant was used (pH5, 32°C). The result is shown in Figure 3, which showed that as amount of yeast increases from 0.25%w/v to 1%w/v bioethanol yield increase from 8.75% to 36.25% on the order after 48 hours of fermentation. Further increase in amount of yeast beyond 1%w/v resulted in decrease of bioethanol yield. This may be as a result of more yeast consuming the limited glucose for self-sustenance, thereby resulting in low yield of bioethanol.

Figure. 3: Effect of the amount of yeast on bioethanol yield

Effect of time on bioethanol yield:

This experiment was done to determine the time of which maximum bioethanol yield and the amount of yeast that gave the optimum bioethanol yield and was used for varying the fermentation duration of 1, 2, 3, days bioethanol at temperature of 32°C, pH of 5.0. Figure 4 shows the effect of time on bioethanol yield. It can be seen from the figure that give the best yield 36, 25% at (2 days) 48 hours of fermentation time.

Figure. 4: Effect of time on bioethanol yield

Bioethanol characteristics:

The production of bioethanol alone is not enough, it is necessary to ensure the quality of the product prepared by comparing it with international standards. In general, international standards used to know the quality of bioethanol are ASTM D 4806 and ASTM D 5798. We chose the properties according to the availability of the equipment in the laboratory²¹.

Table.1: The characteristics of the bioethanol product obtained

Characteristics	Bioéthanol	Ethanol
Physical state	Liquid	Liquid
Color	Colorless	Colorless
pH	6.9	6.5-7.0
Density (g/cm³)	0.82	0.79
Boiling Point	78.5 °C	79 °C

The analysis of the results presented in Table 2 shows that Physical State, Color and pH values are in line with European standards. density, boiling point of our bioethanol is close to the ethanol characteristics.

FT-IR spectrometry:

An infrared spectrometer (IR) is an analysis technique used to verify the purity of bioethanol obtained (Fig.5 and Table.2)

Figure.5: IR spectroscopy of bioethanol produced

Figure 4 explain the spectral of bioethanol is identical in the spectral range between 4000 and 400 cm^-1.It is found that the spectrum shows a wide band at 3385.707 cm^-1 which represents the elongation of the group O-H²³.They also have two bands medium and low in 2970,113 and 2895, 527 cm^-1 corresponding to the elongation of the CH₃ bond of CH₃ and CH₂, the elongation of the C-C bond (linear chain) that is confirmed by a mean peak at 881cm^-1. Finally, we observe that the intensities of the absorbance at the specific strong band at 1050 cm^-1 corresponding to the elongation of the C-O bond of a primary alcohol²⁴. The table 2 shows the results of the bioethanol basebands by IR, we notice similarities between the bands and the spectrum, indicating that our product conforms to international standards.

Table 2 Most important absorption bands of the mid-infrared spectra of bioethanol

Wavenumber (cm⁻¹)	Vibration
3385	O-H stretching of bonded and non-bonded hydroxyl groups
2975	Asymmetric C-H stretching
2896	Symmetric C-H stretching
1650	O-H bending
	Conjugated C-O stretching
1454	C-H deformation
1429	C-H deformation
	CH₂scissoring
1384	Symmetric C-H deformation
1337	C-H vibration
	CH₂wagging
1090	C-O stretching
1053	C-O stretching

CONCLUSION:

In conclusion, from the results obtained for this research showed that we can dates of “Degla Bayda” as a lowcost feedstock for bioethanol production and can be conclude that commercial S. cerevisiae can use for bioethanol production and the best optimum fermentation conditions obtained at temperature 32°C, pH 5.0, yeast ratio 1g and fermentation time of 48 hours (2 days), bioethanol yield of 36.25% was obtained.in accordance with this study, developing countries can produce clean bioenergy from the natural resources Untapped they have in their daily life.

ACKNOWLEDGEMENTS:

We acknowledge the Process engineering Laboratory, Kasdi Merbah University, Ouargla, Algeria, for their help in chemical analysis. The authors would like to thank the director and members laboratory of Valorisation and Promotion in Saharan Resources for supporting this research.

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Received on 01.06.2021 Modified on 21.06.2021

Asian J. Research Chem. 2021; 14(5):375-379.

DOI: 10.52711/0974-4150.2021.00064