**4.12 Animal feed**

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

strain P4, which formed 21.50 g (dry weight) of biomass per litre of undiluted wastewater after 20 days of cultivation. This and other strains also carried out an outstanding reduction of the COD and the phenolic content of OMW, as well as a pH raise (Robles et al. 2000). The *Y. lipolytica* strain ATCC 20255 strain has been effective in the treatment of OMWW that

Microalgal biomass is as a potential source of proteins, carbohydrates, pigments, lipids, and hydrocarbons. In addition, the biomass can be used as a low-release fertilizer. This chemical composition has great variation, depending on the species, culture medium, and the operating conditions. Microalga *Scenedesmus obliquus* was used to biomass production from rinse water (RW) from two-phase centrifugation in the olive-oil extraction industry. Maximum specific growth rate, 0.044 per hour was registered in the culture with 5% RW and reduces 67.4% BOD when operating with 25% RW. The greater specific rate of protein synthesis during the exponential phase was 3.7 mg/g h to 50% RW (Hodaifa et al. 2008).

Microbial lipid (single cell oil or SCO) production has been an object of research and industrial interest for more than 60 years. Microorganisms can store triacylglycerol (TAG) as intracellular oil droplets. *Gordonia* sp. DG accumulated more than 50% lipid with most tested wastes, while only 29, 36 and 41% was accumulated in presence of olive mill waste,

Carbon-limited cultures were performed on waste cooking olive oil, added in the growth medium at 15 g/l, and high biomass quantities were produced up to 18 g/l. Cellular lipids were accumulated in notable quantities in almost all cultures. *Aspergillus* sp. ATHUM 3482 accumulated lipid up to 64% (w w) in dry fungal mass. In parallel, extracellular lipase activity was quantified, and it was revealed to be strain and fermentation time dependent, with a maximum quantity of 645 U/ml being obtained by *Aspergillus niger* NRRL 363. Storage lipid content significantly decreased at the stationary growth phase (Papanikolaou et al. 2011).

Composting is the aerobic processing of biologically degradable organic waste to produce a reasonably stable, granular material and valuable plant nutrients. Composting removes the phytotoxicity of the residues within a few weeks and allows the subsequent enrichment of croplands with nutrients that were originally taken up by olive tree cultivation. Composting of OMWs requires the proper adjustment of pH, temperature, moisture, oxygenation and nutrients, thereby allowing the adequate development of the microbial populations

Among the possible technologies for recycling the TPOMW, composting is gaining interest as a sustainable strategy to recycle this residue for agricultural purposes. Dry olive cake alone or mixed with municipal biosolids vermicomposted for 9 months in order to examine the behaviour of three specific humic substance-enzyme complexes. During the process, βglucosidase synthesis and release was observed, whereas no significant change in urease and phosphatase activity was recorded. The vermicomposted olive cake, alone or in blends with biosolids, could be effectively used as amendment due to their ability to reactivate the

Olive pomace, a wet solid waste from the three-phase decanters and presses, was composted by using a reactor for a period of 50 days in four bioreactors. Urea was added to

C, P and N-cycles in degraded soils for regeneration purposes (Benitez et al. 2005).

yield of the biomass (single-cell protein) was 22.45 g/l (Scioli and Vollaro 1997).

hydrolyzed barely seeds and wheat bran, respectively (Gouda et al. 2008).

**4.11 Compost** 

(Arvanitoyannis and Kassaveti 2007).

Treated OMW may find applications as a raw material in various biotechnological processes or as animal food. The appropriate utilization of by-products in animal nutrition can improve the economy and the efficiency of agricultural, industrial and animal production.

The olive pomace was alkali-treated, transferred to culture flasks and inoculated with the above fungi. After inoculation, the fermentation process was carried out at 25°C for 60 days. The results indicated that *Oxysporus* spp. degraded lignin up to 69%, whereas *Phanerochaete chrysosporium* and *Schizophyllum commune* delignified olive pomace 60% and 53%, respectively. However, the potential use of treated olive pomace as a feed for poultry is still under investigation. The fermented olive pomace can be used as a feed for the poultry industry (Haddadin et al. 2002).
