Authors
Abstract
This study focuses on producing single cell protein from petroleum fraction (ethanol, kerosene,
gas oil) by growing two types of microorganisms (Candida sp. and Bacillus subtilis) on these
materials as energy and carbon source , These two types of microorganisms are isolated from
contaminated soils cv with petroleum derivatives brought from AL-Dorah and Beji refineries , fuel
stations ,and garages . At the first stage the microorganisms are cultivated on different media (blood
and nutrient agar ) and on mineral salt medium (MSM) to identify on genus of each type . After this
, the microorganisms are grown on different concentrations of ethanol , kerosene , gas oil (0.5, 1.0,
2.0, 3.0, 4.0 ( v/v)% ) at 7.4 pH and 32°C temperature . In the second stage the microorganisms are
growing in still liquid culture at the same conditions . In this stage the yield percent, number of cell
per milliliter , and biomass weight are calculated for either type of microorganisms. Composite
rotatable Box –Wilson experimental design is adopted to design the experimental work .
Statistically , the response functions (i.e. yield percent of ethanol , kerosene , gas oil ) are related to
the most effective variables on single cell protein (SCP) production . The temperature is fixed at
32°C at this stage also, because the range of temperature growth of these microorganisms is narrow
(30 to 34°C) , where there is no significant effect at this range of temperature. Concentration and
pH are ranged between 0.5to 4.0% and 7.0to9.0 respectively . Optimum conditions are determined
and found equal to 7.36 for pH and 1.31% for concentration for ethanol , 7.42 and 4.0% for
kerosene, and 7.51 and 4.0% for gas oil .The percentage of crude protein was evaluated according
to Kjedhal method . The maximum protein content was 61.25% which was closed to the results
obtained by previous studies. The bioassay was carried out using chicken embryos , where chicken
eggs were used for this purpose. The result of bioassay was 83.5% of successful eggs , which is
acceptable with the percent given by Kohen Lee.The last stage is designing a batch bioreactor and
calculating all process parameters depending on the results of experimental work in pervious stages
, In general , the characteristics of (SCP) production using two types of microorganisms are agreed
well with general characterization of (SCP) production that accommodates the general concepts of
(SCP) production .
Keywords
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