PRODUCTION OF Candida BIOMASSES FOR HEAVY METAL REMOVAL FROM WASTEWATERS

Abstract

Yeasts can accumulate heavy metals and grow in acidic media. In the present study, it was shown that Candida yeasts in an aqueous solution accumulate single Cu(II) and Ni(II) cations. The effect of heavy metal ions on the specific growth rate of biomasses and the uptake of metal ions during the growth phase was investigated in a batch system. Bioaccumulation efficiency decreased with increasing metal ion concentrations at constant sucrose concentrations. Both the specific growth rate and the biomass concentration were more inhibited in the bioaccumulation media containing Ni(II) ions singly as compared with the bioaccumulation media containing Cu(II) ions singly. The maximum specific growth rate and the saturation constant of yeasts were examined with a double-reciprocal form of Monod equation. Metal uptake performance decreased from 81.68% to 46.28% with increasing Ni(II) concentration from 25 mg/L to 250 mg/L for Candida lipolytica. Candida biomasses may be an alternative way of removal of heavy metals from wastewaters and may constitute a sample to produce new biomass. The study showed that Candida yeasts can be used as economical biomass due to their metal resistance and efficient production.Özet: Mayalar, asidik ortamda büyüyebilir ve ağır metalleri biriktirebilir. Bu çalışma, Candida türü mayaların sulu çözeltilerden tekli Cu(II) ve Ni(II) katyonlarını biriktirdiğini göstermiştir. Ağır metal iyonlarının, biyokütlelerin spesifik büyüme hızı ve büyüme periyodu boyunca metal iyonlarını giderimi üzerindeki etkisi, bir kesikli sistemde araştırılmıştır. Sabit sakaroz derişiminde, metal iyonu derişimi arttıkça, biyobirikim verimi azalmıştır. Hem spesifik büyüme hızı hem de biyokütle konsantrasyonu, tek başına Cu(II) iyonları içeren biyoakümülasyon ortamına kıyasla Ni(II) iyonları içeren biyoakümülasyon ortamında daha fazla inhibe edilmiştir. Mayaların maksimum özgül büyüme hızı ve doygunluk sabiti, Monod denkleminin çift-karşılıklı formu ile incelenmiştir. Candida lipolytica'nın metal giderim performansı Ni(II) derişiminin 25 mg/L'den 250 mg/L'ye çıkmasıyla % 81,68'den % 46,28'e düşmüştür. Candida biyokütleleri, ağır metallerin atık sulardan gideriminde alternatif bir yol olabilir ve yeni biyokütle üretimi için bir örnek oluşturabilir. Bu çalışma, Candida mayalarının, metal direnci ve verimli üretimleri nedeniyle ekonomik biyokütle olarak kullanılabileceğini göstermektedir.

The Effects of Heavy Metals and Molasses on Enzyme Activity of Candida Yeast

“…Saturation kinetics were used to determination of the relevance of specific growth ratesubstrate concentration. Detail results were presented in our previous study [29].…”

“…Sugar factory which is in main Ankara (Turkey) donated molasses sucrose. Molasses consisting of 47-48% sugar was applied as the one carbon source of the yeasts for microbial growth [29].…”

“…All experiments were conducted at pH:4 and 25 o C. Details of the adaptation experiments of the yeasts were discussed in our previous study. Microorganism concentration, residual Cu 2+ and Ni 2+ concentrations were determined at 360, 460 nm and 340 nm, respectively [29].…”

“…Lipase determination using living biomass, the chemical nature of metal ions plays an important role. Apart from essential trace metals for metabolic activities of microorganisms, higher concentrations of heavy metals might be deadly toxic and can be inhibited to enzyme activity [29,36].…”

“…For this reason, enzymatic techniques in water treatment have gained more attention because of specific properties such as enantiomeric, regional selectivity and substrate specificity [28]. Due to the Candida biomass can bioaccumulate metal ions, produce lipase enzyme and growth in metal contained media, uptake of Cu 2+ and Ni 2+ ions were investigated with changing molasses sucrose and Cu 2+ and Ni 2+ ion concentrations in our previous study [29]. We observed that biomass concentrations and specific growth rates increased when initial molasses sucrose concentration were increased in a medium containing metal and metal-free media.…”