كليدواژه :
اتوتروف , بيوليچينگ , تراكم آهن و گوگرد , معدن ميدوك
چكيده فارسي :
يكي از شاخص هاي مهم در ارتباط با صنعت، اقتصاد و محيط زيست دستيابي به بيشترين باز يابي با حداقل هزينه و كمترين ميزان آلودگي است.امروزه استفاده از ميكروارگانيزم هاي كموليتوتروف مزوفيل در استخراج فلزاتي چون مس، اورانيوم، طلا، كبالت و موليبدن معروف به پديده استخراج بيولوژي در سنگهاي كم عيار معمول شده است. هدف از انجام اين تحقيق شمارش دو دسته مهم از باكتري هاي اكسيد كننده آهن وگوگرد در مناطق مختلف معدن ميدوك شهربابك در استان كرمان مي باشد. براي دستيابي به اين هدف از هفت نقطه مختلف معدن ميدوك نمونه هاي خاك جمع آوري شد. تعداد باكتري هاي اتوتروف اكسيد كننده آهن و گوگرد با تهيه سريال رقت از نمونه ها و كشت در محيط نه كي حاوي آهن و گوگرد عنصري بترتيب انجام شد. باكتري هاي هتروتروف نيز با كشت در محيط نوترينت براث شمارش شدند. تعداد حداكثر احتمالي باكتري هاي اتوتروف و هتروتروف نيز با كشت رقت هاي اعشاري از نمونه ها در محيط اختصاصي درون ميكروپليت هاي 24 خانه انجام شد. نتايج حاصل از اين تحقيق نشان داد كه بيشترين ميزان باكتري هاي هتروتروف مربوط به YP نمونه خاك زرد رنگ نزديك به تشتك PLS و كمترين تراكم باكتري هاي هتروتروف در نمونه OP پد اكسيدي بود. بالاترين تراكم اكسيدكننده هاي آهن مربوط به نمونه OP پد اكسيدي بود و كمترين تراكم نيز مرتبط به YP نمونه خاك زرد رنگ نزديك به تشتك PLS بود. تنوع نسبتا پاييني در نمونه هاي معدن در خصوص اكسيدكننده هاي آهن وجود داشت. بالاترين تراكم اكسيد كننده هاي گوگرد مربوط به YP خاك هاي زرد رنگ اطراف تشتك PLS بود وكمترين تراكم باكتري هاي اكسيد كننده گوگرد مربوط به OP پد اكسيدي معدن بود. تنوع مناسبي از انواع اكسيدكننده هاي گوگرد در معدن ميدوك در مقايسه با اكسيدكننده هاي آهن وجود دارد. با بكارگيري نتايج حاصله از اين تحقيق و باكتري هاي اتوتروف بدست آمده مي توان جهت افزايش فرايندهاي بيوليچينگ در معدن ميدوك بهره برد.
چكيده لاتين :
Introduction: One of the most important indicators in relation to industry, economy and environment is to
achieve the most recovery with the least cost and minimum pollution. Today, the use of chemolithotrophic
microorganisms is common for extraction of some metals such as cooper, uranium, gold, cobalt and
molybdenum in bioleaching process of low-grade rocks. Attention to the bioleaching of heavy metals such as
copper, nickel, cobalt, zinc, and molybdenum has been increased in recent years because of its application to
low-grade ores. The variety of microbes identified as being capable of growth in situations that simulate biomining
commercial processes is rapidly growing. This is partly because of an increase in the number of
environments being screened for such organisms, partly because of an increase in the variety of minerals being
tested, and most importantly because of new techniques available to screen for the presence of organisms. The
aim of the present research was to study the quantity of two important autotrophic bacteria, iron and sulfur
oxidizing bacteria, in different regions of Miduk mine in Shahrbabak, Kerman province.
Materials and Methods The soil samples were collected from different locations of Miduk cooper mine
such as: Sulfuric Pool Acid Discharge (PAD), Oxidic PAD, Sulfuric damp, Pool Leaching Sulfuric (PLS)and
leaching hip. Top layer of mine soil (about 1 cm) was removed. In each site, soil samples were collected from
five different spots. The quantity of iron and sulfur oxidizing bacteria were measured by culture of serial
dilutions of samples in 9K medium with Iron and sulfur as electron sources, respectively. The 9K medium was
used for enrichment of iron and sulfur oxidizing bacteria in collected mine samples. These two important groups
of bacteria have autotrophic growth but the energy sources for these two bacteria are different. Iron oxidizing
bacteria use ferrous ion in form of FeSO4 but sulfur oxidizing bacteria use inorganic sulfur and sulfur
compounds as a source of energy and obtain the carbon from the reduction of the CO2 of the atmosphere, in
autotrophic growth. Heterotrophic bacteria were quantified by culture in nutrient broth medium. Most probable
number (MPN) method was used to enumeration the autotrophic and heterotrophic bacteria by culture of samples
in 24 well microplates with specific medium. The positive index for enumeration iron and sulfur oxidizing
bacteria in these experiments were red color and turbidity, respectively. The microplates were incubated for 21
days for autotrophic bacteria and 7 days for heterotrophic bacteria.
Results and Discussion: The results of this research showed that the highest quantity of heterotrophic
bacteria related to soil near to PLS and the lowest quantity belonged to sulfuric PAD. Iron oxidizing bacteria had
the highest density on oxidizing Pad (OP) and the lowest density of these bacteria found in soil near to PLS. The
diversity of iron oxidizing bacteria was low in the mine. The lowest quantity of sulfur oxidizing bacteria related
to oxidizing PAD. Although appropriate diversity of sulfur oxidizing bacteria in compare to iron oxidizing
bacteria was observed in the Miduk mine. These results about quantity of iron oxidizing bacteria confirmed this
truth that the presence of oxygen and also low acidity in oxidizing Pad (OP) has major effect on the distribution
and quantity of iron oxidizing bacteria. Because, the optimum condition for growth of iron oxidizing bacteria is
low acidity and abundance of oxygen that these two factors provided in oxidic Pad (OP).
The quantity of sulfur oxidizing bacteria was high in yellow soil near to PLS. These results obtained by
enumeration with MPN and Newbar lam methods. This result can be interpreted as the high concentration of
sulfur element in this region has a selection force to prevalent the sulfur oxidizing bacteria in compare to iron
oxidizing bacteria in this region. Because, when the sulfur is high, the bacteria that can use this element as their
only energy source for fixation of CO2 is dramatically increased.
Conclusions: In the present research, the quantity and distribution of iron and sulfur oxidizing bacteria of
Miduk cooper mine were studied. Based on the results, iron and sulfur oxidizing bacteria had the highest density
on oxidizing Pad (OP) and in yellow soil near to PLS, respectively. Although sulfur oxidizing bacteria had an
appropriate diversity compared to iron oxidizing bacteria in Miduk mine. However, the results obtained in this
study confirmed that the sufficient quantity of iron and sulfur oxidizing bacteria were present in this mine. Then,
the soil bacteria of this mine can be used to enhance the bioleaching process in Miduk mine.
