Heavy Metal -Induced Oxidative Stress And Alteration In Secretory Proteins In Yeast Isolates

In the recent years, yeasts have evolved as potent bioremediative candidates for the detoxification of xenobiotic compounds found in the natural environment. Candida sp. are well studied apart from Saccharomyces in heavy metal detoxification mechanisms. In the current study, Candida parapsilosis strain ODBG2, Candida sp. strain BANG3 and Candida viswanathii strain ODBG4 were isolated from industrial effluents and contaminated ground water were studied for their metal tolerance. Among these three isolates, the metal tolerance was found to be more towards Lead (Pb 2mM), followed by Cadmium (Cd 1.5mM) and Chromium (Cr(VI), 1mM). On further exploring the involvement of primary defensive enzymes in these isolates exhibited towards metal tolerance, the anti-oxidative enzyme Superoxide dismutase (SOD) was found to be prominently high as 25% during first 24h of metal-isolate interaction. In the Catalase (CAT) enzyme assay, it was observed that, the increased enzyme activity at 48h also triggered the activity of peroxidases (PO), which lead to the increase in reduced glutathione (GSH) in the organism by 0.87-1.9 folds, as a metal chelator and also as a second line of defensive molecule. The exoproteome profile showed the early involvement (exponential growth phase) of secreted proteins (low molecular weight) of about ~40-45kDa under Cd and Pb stress (0.5mM). The exoproteome profiling under heavy metal stress in Candida parapsilosis strain ODBG2 and Candida viswanathii strain ODBG4 is the first report.

Use of agro-industrial residues for lipase production by Candida viswanathii in a solid-state cultivation system

Lipases are an important group of enzymes that catalyze the hydrolysis of triacylglycerol and there are many industrial applications. The aim of this work was to produce the lipase by the yeast Candida viswanathii using solid state culture with agro-industrial wastes (barley bagasse, corn husk, corncob, soybean seed coat and soybean husk). The biomass pretreatment methods were evaluated, as well as the media supplementation with nitrogen and mixing substrates. Also, the efficiency of olive oil and poultry fat was evaluated on the induction of lipase production, followed by the scale-up from 20 g to 100 g. The enzyme activities in the cultures without pretreatement were higher when soybean seed coat supplemented with both olive oil (7.06 U/gss) and poultry fat (8.40 U/gss) were used. However, the pretreated substrates did not demonstrate a satisfying induction of lipolytic activity. From the nitrogen sources, yeast extract showed an increase of approximately twice the original production with both olive oil (18.12 U/gss) and poultry fat (15.98 U/gss) supplementation. On the scale-up step, the results demonstrated that, for the 20 g culture, the best lipase production was observed on the 7th day (33.52 U/gss), while for the 100 g culture the highest lipase activity was after 5 days (17.88 U/gss). The cultivation of ground soybean skin without pretreatment supplemented with yeast extract as a source of nitrogen, with fresh barley bagasse and poultry fat was the best combination.

LIP4 gene expression from Candida viswanathii strain

Background : Lipases are hydrolases that catalyze the cleavage of triglyceride esters bonds, releasing glycerol and free fatty acids. Candida genus can produce distinct isoforms of lipase, among of them, Candida viswanathii strain is a potential lipase producer using hydrophobic carbons sources in which produced high level of enzyme under submerged cultivation using olive oil as carbon sources. This enzyme has commercially attractive due to characteristics desired in the industries processes. The genes responsible for encoding the lipases comprise a family called LIP gene. C. viswanathii not have its genome sequenced and are not available in annotated form through the GenBank nucleotide sequence database for lipase production. The aim of this work was understanding at molecular level the effect of carbon sources to lipase production, to identify and to analyses the gene expression of CvLIP4 from C. viswanathii on different culture media. Results : In silico analysis was carried out with LIP4 gene from Candida species. Degenerate primers were designed and evaluated for expression in different conditions. CvLIP4 expression was evaluated using carbon sources glucose, tributyrin, triolein and olive oil. Triolein and olive oil were strong inducer for CvLIP4 gene expression, while tributyrin was a weak inducer and glucose was strong repressor. Conclusions : These results will contribute to further studies about regulation of the lipase genes expression from C. viswanathii and heterologous expression of this enzyme to improve the catalytic conditions in industries processes.