University of Khartoum Journal of Agricultural Sciences

Screening and Molecular Characterization of Oleaginous Yeasts and Their Potentiality for Single Cell Oil Production

Rania. A. Elmahe — 2022-11-11

The study aimed to isolate oleaginous yeasts from different sources (rotten fruits, fruit juices, milk, fish and air) and to identify and to study the possibility of production of single cell oil (SCO) from wheat straw and sugarcane molasses media. Thirty samples of yeasts were isolated using different methods according to the source of isolates. The isolated yeasts were characterized using microscopic appearance, colony morphology, physiological tests, assimilation tests and molecular identification. The effectiveness of oleaginous yeast to produce the single cell oil was studied, by growing the yeast on two types of wheat straw media (detoxified liquid hydrolysate (DLH) and non-detoxified liquid hydrolysate (NDLH)), and molasse media. Single cell oil was extracted by hexane. Eighteen isolates were found to be yeast, and the profile of ten yeast samples was identified as Saccharomyces cerevisiae, while, one sample was identified as Pichia guilliermondii. DLH wheat straw gave higher productivity of oil than NDLH wheat straw. Generally, S. cerevisiae gave higher oil productivity (84 %), compared to P. guilliermondii (52 %).

Physicochemical Properties of Single Cell Oil Extracted from Oleaginous Yeasts

Rania. A. Elmahe — 2022-11-11

The study aimed at extracting single cell oil (SCO) from some oleaginous yeasts living on wheat straw and sugarcane molasses media and to determine physicochemical properties of the produced oil for further assessment as edible oil. Thirty samples of yeasts were isolated according to the different methods based on the source of isolates. The effectiveness of oleaginous yeast to produce the single cell oil was studied, when the yeast was grown on two types of wheat straw media (detoxified liquid hydrolysate (DLH) and non-detoxified liquid hydrolysate (NDLH)), and molasse media. Single cell oil was extracted by hexane. Saccharomyces cerevisiae and Pichia guilliermondii were used to produce SCO. SCO produced from oleaginous yeasts in sugarcane molasses media was significantly (P≤0.05) higher than that produced in wheat straw media. DLH of wheat straw gave higher productivity of oil than NDLH wheat straw. Generally, S. cerevisiae gave higher oil productivity (84 %), compared to P. guilliermondii (52 %).The results indicated that most of the physicochemical properties of extracted oil were found to be within the recommended limit of the common edible oil reported, except for the iron content; it ranged from 21 to 24 mg/kg, which was 4-5 times more than the permissible level of that of the Codex Alimentarius Commission. In addition, single cell oil produced by molasses contained omega-3 fatty acids such as eicosapentaenoic and docosahexaenoic which are not found in vegetable oil. Also the unsaturated fatty acids of SCO produced in wheat straw media were higher than that produced in molasses media. The fatty acid profile of SCO produced in molasses media was different from that of vegetable oils. The good physicochemical characteristics and fatty acids profile of SCO from wheat straw make it safe and a promising potential raw material for production of edible oil. The result of this study suggests the isolation of oleaginous yeast in order to be used in the edible oil production

Assessment of Litter Input, Decomposition and Elements Dynamics in Yatta Tropical Forest in Western Equatoria State, South Sudan

Daldoum M.A — 2022-11-11

This study characterized soils, assessed litter input, litter decomposition and elements release in Yatta forest, Western Equatoria State, South Sudan during May 2008 and March 2010. The soil was described and sampled. Litter was collected weekly from plots of 16 m² under the forest cover with forty replicates. Seventy five litter bags were buried at 15-30 cm soil depth to assess decomposition and elements' release. Twenty fife bags were withdrawn at every 6, 12 months periods Fallen litter, remaining decomposed litter and soil samples were analyzed in the Laboratory of the Department of Soil and Environment Sciences, Faculty of Agriculture, University of Khartoum. The soil was characterized as Oxisols, sandy clay loam, acidic, rich in organic matter, and amply furnished with nutrients. Litter input was 1791 kg/ha/year; with concessive seasonal maxima and minima in dry and wet months. Losses of dry matter were high, ranging of 52.2 % to 96.8 % during the tested periods. The elements K, N, P, Ca, Mg were rapidly released with successive rates ranges of 37 %-62 %, 56 %-72 % and 62 %-90 % during 6, 12 and 18 months observation periods. The results showed a high potential fertility of this natural forest site which will support the sustainability of the growing stock and utilization of the forest for high yielding food crops.

Survey and Molecular Identification of Xanthomonas euvesicatoria Causing Bacterial Spot of Tomato in Blue Nile State in Sudan

Soad Ali Eltayeb Algam — 2022-11-11

This study aimed to survey, characterize, and identify the causal pathogen of tomato bacterial spots (TBS). The survey evaluated the disease incidence and severity on tomato cultivated in Blue Nile State during the autumn season 2015. The surveyed sites were in Alrosseris and Aldmazein localities. Four farms were selected from each locality. Symptomatic leaves were collected and sent to plant pathology laboratory, Department of Crop protection, Faculty of Agriculture, University of Khartoum for detection of the pathogen. Pathogenicity of the isolated bacteria was confirmed by relevant test. The pathogen was isolated and characterized morphologically, biochemically and at molecular level. The survey revealed that there was no significant difference in disease incidence within each locality, while there were significant differences (P ≤ 0.05) among locations within both localities in disease severity. The disease incidence was remarkably high in Alrosseris and Aldamazein which recorded 49.27 and 52.17 %, respectively, while the disease severity was 28.28 and 30.32%, respectively. The results showed that the isolates were rod shaped, obligate aerobic, Gram negative, catalase positive, oxidase negative, and were able to hydrolyse starch and gelatine, yellow colonies on nutrient agar and Yeast Dextrose Calcium carbonate (YDC) media. In the pathogenicity test, the bacterium known as Xanthomonas vesicatoria was confirmed to be as Xanthomonas euvesicatoria by PCR and sequence analysis of the 16S RNA gene (Gen Bank Accession No's MH047248, MH051263 and MG686236).These results also indicate that the tomato plants grown in Blue Nile State were highly infected by the bacterial leaf spots. Further studies should be considered to determine potential yield loss caused by the pathogen, as well as control strategies to limit the spread of this pathogen. To our knowledge, this is the first report of Xanthomonas euvesicatoria causing bacterial spot disease in tomato in Sudan

Effect of Irrigation System and Irrigation Interval on Seed Yield and Water Productivity of two Soybeans (Glycine max L. Merr.) Cultivars under Drip and Furrow Irrigation in Eastern Sudan

Ahmed Babikir Ahmed — 2022-11-11

Water stress is one of the limiting factors of soybean yield in eastern Sudan. The objective of this study was to obtain basic information on soybean cultivation using two irrigation systems in eastern Sudan. This study examined the leaf area index, yield and irrigation water productivity (IWP) response using two soybean cultivars: Sudan₁ (V₁) and Sudan₂(V₂) under drip (DS₁) and furrow (DS₂) irrigation systems. The experiment was carried out in the summer seasons of 2016 and 2017. Three irrigation intervals, every 4, 8 and 12 days designated as W₁, W2 and W₃, respectively, were used. A randomized complete block design was used as strip-split plot arrangement with three replications. The data were statistically analyzed using STATISTICS 10; mean separation was computed using LSD. The results showed that cultivar Sudan₁gave higher leaf area index values under four days irrigation interval particularly with furrow irrigation system. Four days irrigation interval treatment increased seeds yield by more than 2.5 % relative to 8 days irrigation interval and 34 % relative to 12 days irrigation interval, as average for both seasons. Drip irrigation system significantly (P ≤ 0.05) increased IWP compared to furrow irrigation system. Highest water productivity was obtained under four days irrigation interval. Eight days irrigation interval significantly (P ≤ 0.05) inhibited the positive effect of irrigation system on seed yield and IWP. The study concludes that IWP for drip irrigation, in both seasons, was 20.5 % higher than furrow irrigation. However, mean seed yield for furrow system, in both seasons, was 25.6% higher than drip irrigation system.

A Note on the Effect of Storage on Physicochemical Properties of Baobab (Adansonia digitata L.) Seedsʼ Oil from Kordofan and Blue Nile States

Alia Mutasim Ali Ibrahim — 2022-11-11

Baobab (Adansonia digitata L.) is an indigenous forest tree related with the Savannah dry lands of sub-Saharan Africa. Local communities utilize the leaves, pulp, and seeds of Baobab as a source of nutrition and for income generation. Seed oil has been used for centuries by rural communities as food and medicine. The global demand for Baobab seed oil in industrial applications has increased in recent years. The present study was conducted to determine physicochemical properties, mineral content and effect of storage on seeds from two different geographical locations (Kordofan and Blue Nile States). Six different samples of Baobab seeds were collected, prepared and stored in 2017 at room temperature until analysis in 2019. The oil was extracted by cold pressing process and its physicochemical properties were evaluated by standard and established methods. The results showed that the Baobab oil color was golden yellow/ reddish yellow and it showed resistance to change in color and seeds contained reasonable amount of oil. Oil density, PH, refractive index and acid value showed negligible change with the storage. However the peroxide value increased when the storage period increased, while the iodine value, saponification and viscosity of the oil decreased markedly with the storage time. Kordofan seed oil was higher than Blue Nile in density, oil content and saponification value, while Blue Nile seed oil showed higher viscosity, peroxide value and minerals especially potassium content.

A note on Microbiological and Biochemical Evaluation of ʻOmtiganiaʼ, a Sudanese Fermented Food Based on Peanut Seed Cake

Siham Eltayeb Mohamed Ali — 2022-11-11

The objectives of this study aimed to evaluate the microbiological and biochemical changes during the fermentation of peanut (Arachis hypogaea) seed cake. The microflora during fermentation was dominated by a homo fermentative lactic acid bacterium (Streptococcus sp and lactobacillus sp) initially, the yeasts and mould and acetic acid bacteria were also present. The accumulation of acids led to the decline of the pH of the mixture from 5.7 to 3.6 on the seventh day of fermentation. Dried ʻOmtiganiaʼ possessed a crude protein content of 67 %. The microbiological analysis showed that the microbial population is mainly bacteria.