Date of Award
Master of Science (MS)
Dr. M. H. Soliman
Dr. Ali Hassan Khalil
Dr. Mousa All Ahmed
The potential threat of whey pollution to the soil environment and ultimately groundwater resources in UAB promoted the elements of concern to the utilization of the whey waste. This work was conducted in AI-Ain area to isolate new fermenting yeast strains, from local soils, capable of fermenting whey lactose.
Soil samples were collected from two locations in AI-Ain area (near Al-Ain dairy farm & AI-Markhania area) and from a neighboring area (AI-Buraimi) based on the soil nature and ecological parameters. Inorganic elements and organic residues of the soil samples were characterized. Results indicated that AI-Buraimi soil is rich in nitrate nitrogen, reactive iron (878 mg kg-1), sulphur and organic carbon. Al-Ain Dairy Farm soil is rich in ammonia nitrogen (26mg Kg-1) and magnesium oxide. AI-Markhania soil is rich in phosphorus and potassium.
Organic analysis indicated that AI-Markhania soil is the richest in organic residuals of plant debris. This results in providing the most favourable organic environment for the growth and proliferation of microorganisms. The highest soil conductivity was recorded in AI-Buraimi area (1.0740dS m-1). This is attributed to the high content of soil minerals. The pH value indicated that all the soil samples were within the neutral to slightly alkaline range [7.10-7.80]. The type of whey used in the study was classified according to pH (6.62) and acidity (0.10%) as sweet whey and the salt content was found to be 0.20%.
Standard and enrichment isolation methods in which the whey lactose is used as a carbon source were used to isolate the potential whey-fermenting yeasts from the soil. The highest number of isolated yeasts was obtained from AI-Markhania soil (rich in organic matter), followed by AI-Buraimi soil (rich in minerals). The lowest number of yeast has been observed in AI-Ain Dairy Farm soil which is poor in. organic nutrients (non cultivated desert soil). Yeast isolates number (2, 1 4 and 20), all isolated from AI-Markhania soil, have shown strong fermentative ability on whey broth. Out of these three isolates, the highest ethanol concentration was achieved by the yeast isolate (number 20). It was tentatively identified to species level in accordance to morphological, cultural, sexual and physiological criteria as described by Barrnet, (1984). The identification of isolate number (20) was confirmed by the National Collection of Yeast Cultures (NCYC, UK) and as a result of this study, it has been referred to as Kluyveromyces marxianus NCYC 2886.
Yeast fermentation conditions [temperature and whey lactose concentrations] were studied so as to reach optimal ethanol yields. K. marxianus NCYC 2886 was subjected to various temperatures ranging between 30°C to 50°C. The results revealed that ethanol production increases in parallel with the elevation of temperature from (30°C, 35°C, 40°C and 45°C). The optimal ethanol production was achieved at 40°C. Therefore it could consequently be referred to as a thermotolerant whey fermenting yeast. Reduction of ethanol production was observed at high temperatures exceeding 50°C.
Eight lactose concentrations, in whey, in the range of 0.31 - 11.05%, were employed to investigate the effect of lactose concentrations on the fermenting ability and efficiency of the yeast strain Kluyveromyces marxianus NCYC 2886 in producing ethanol. The optimal lactose concentration found to enhance ethanol production is 2.5% contained in 50% diluted whey. The increase in lactose concentration from 2.50% to 4.95% slightly decreased the ethanol yield and ultimately withstood lactose utilization.
With the aim of optimizing ethanol yield, different chemical amendments were subjected to study so as to test their ability in enhancing whey fermentation at 40°C using 50% diluted whey. Addition of 0.20 g of yeast extract in 100 ml of 50% whey concentration resulted in yielding 6.55% ethanol compared to the non-amended whey (5.33%). This was the highest yield of ethanol obtained. Ethanol concentrations were found to be similar (6.10%) when 1.20 g/100 ml whey of both beef extract and peptone were used. Addition of 0.03 g of potassium di-hydrogen phosphate (KH2PO4) resulted in producing 6.35 % ethanol. The above supplements are significantly increased the ethanol production and considered as enhancers.
In contrast, the addition of higher concentration of yeast extract (1.20 g) significantly decreased ethanol yield to 3.80% compared to the non-amended whey · (5.33%). A clear inhibition of ethanol yield was observed when magnesium sulphate (MgSO4) alone was used as a supplement in whey fermentation. Urea has shown inhibitory effect on whey fermentation by the yeast strain K. marxianus NCYC 2886. Di-potassium hydrogen phosphate (K2HPO4) ions appeared to exert a significant inhibitory effect on fermentation process compared to the non-amended whey
(5.33%). on addition of mesoinositol (0.10% w/v) and pantothenate (0.0001% w/v) the ethanol concentrations yield were 3.57% and 3.55%, respectively. Calcium carbonate (CaCO3) (0.20% w/v) led to the production of 3.99% ethanol which is significantly low compared to the non-amended whey (5.33%). Manganese chloride (MnCl2) added to 50% cheese whey (final concentration was 1.0 g/L) resulted in low production of ethanol at 40°C (3.53%). This result may be attributed to the addition of higher concentration of Mn Cl2. The addition of high linoleic acid concentration (1 % w/v) to 100 ml of 50% whey resulted in obvious reduction of ethanol production where 3.55% ethanol was yielded.
The results obtained by using riboflavin (0.000 1 % w/v), pyridoxin-HCl (0.0001 % w/v), aminobenzoic acid (0.0002% w/v), malt extract (0.2% w/v), ammonium sulphate [(NH3)2SO4] (0.05% w/v), Tween 80 (30 µL), nicotinic acid (0.0005 % w/v), thiamin (0.0001 % w/v), peptone (0.20% w/v) and beef extract (0.20% w/v) indicated no significant effect on the whey fermentation process at 40°C compared to the non-amended whey (5.33%).
The reduction efficiency of Chemical Oxygen Demand (COD) obtained for the fermented 50% whey, with and without yeast extract addition at 40°C, were 59% and 46% respectively.
Al Muhairi, Mouza Suhail, "Biotechnology of Whey using Yeast Fungi Isolated from Local Environment" (2001). Theses. 527.