**3. Conclusion**

464 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

Different mixtures of triacylglycerols (Rodriguez et al., 2006): olive, sunflower, corn, peanut, walnut and grape seed oils, were used as energy and carbon sources in addition to lactose, and with urea as nitrogen source. It should be emphasized that the presence of the carbohydrate account for the early growth of the strain *Rhizopus homothallicus* and later growth occurs due to the added oil (Pokorny et al., 1994). This fungal strain was able to produce similar high lipase activities with all studied oils. In the fermentation system, lipase synthesis was not prevented at 4% of triglycerides. To complete these studies, the above medium using olive oil and urea was chosen to evaluate the effect of different carbohydrates on lipase production: glucose, fructose, glycerol, xylose, sucrose and lactose. There were little or no differences with these substrates. This fact suggests that carbohydrate type does not influence lipase production, probably because the carbohydrate concentration is low (5 g/ l) compared to the oil amount (40 g/l) added to culture media and because they are probably utilized

In the study (Hama et al., 2006) utilizing *Rhizopus oryzae* cells as whole-cel biocatalysts, various substrate-relate compounds such as olive oil, oleic acid, oleyl alkohol, methyl carpate and Tween 80 were tested. It was found that the addition of olive oil on lipase production and localization in suspension cells were therefore investigated (Ban et al., 2001). Olive oil increased intracellular lipase production. However that extracellular hydrolysis activity was much higher in the absence of olive oil. Because the *Rhizopus oryzae* cells used in the study were able to produce lipase constitutively regardless of whether substrate-related compounds were present, it seems likely that these compounds are effective in retaining

Nitrogen and carbon sources influencing the growth and production of lipase by *Rhizopus oryzae* were studied by Fadiloglu & Erkmen (1999). High yields of enzyme activity were obtained when protease peptone was the nitrogen source in media with olive oil and without olive oil. Carbon sources increased lipase activity in the media without olive oil, but decreased it slightly in the presence of oil. Lipase activity was significantly higher in the media with olive ail than that without olive ail. Biomass concentration was also higher in the presence of oil (Fadiloglu & Erkmen 1999). Rapid induction of enzymes able to break down foodstuffs appearing in the environment of the micro-organism is clearly of great ecological advantage. This induction process effects a change in the phenotype allowing further

The fungus *Geotrichum candidum* 4013 produces two types of lipases (extracellular and cellbound; Stránsky et al., 2007). Both enzymes were induced by addition of olive oil. The differences in the abilities of these two enzymes to hydrolyze *p*-nitrophenyl esters were observed. Yan and Yan (2008) tested a combination of different experimental designs to optimize the production conditions of cell-bound lipase from *Geotrichum* sp. A single factorial design showed that the most suitable carbon source was a mixture of olive oil and citric acid and the most suitable nitrogen source was a mixture of corn steep liquor and

production of energy required for metabolism and/or growth (Wiseman, 1975).

before the oil and consequently, before lipase production (Cordova et al., 1998).

**2.6** *Rhizopus homothallicus*

**2.7** *Rhizopus oryzae*

lipase within the cells.

**2.8** *Geotrichum candidum*

Inducible enzyme systems in micro-organisms display many features of microbiological and biochemical interest. There is no doubt that in the microbial systems investigated, the major induced enzyme (usually a hydrolase) was fonned *de novo.* Enzyme formation occurs from amino acids, rather than from inactive peptide or protein precursor existing prior to the addition of the inductor to the culture (Wiseman, 1975).

Most published experimental data have shown that lipid carbon sources (especially natural oils) stimulate lipase production. Among vegetable oils, olive oil has been referred as one of the best inductors of lipase production. The review showed that olive oil plays significant role in lipase production. It could be concluded that the higher content of unsaturated free fatty acids contained in oil, the higher intracellular and extracellular lipase activity could be obtained with the oil as inductor for cells cultivation.
