•olive oil cake as the basic nutrient source showed that it could be a good substrate for lipase and protease production in SSF by yeasts Candida rugosa, providing necessary nutrients and physical support for the yeast growth and enzyme production.

•Lipase and protease production could be further improved by careful selection and addition of various carbon and nitrogen sources.

•The fermentation of the olive cake by non-toxic food approved strain may improve the substrate value as animal feed.

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Waste stream characteristics must be understood to tackle waste management problem in Tripoli

city, Libya. It is recognized that information on both quantity and composition of generation waste

is important for the effective planning of household waste handling infrastructure. So, this study is

aimed to evaluating the generation, composition and density of household solid waste in Tripoli

city, Libya. The study is carried out according to the Annex 2.1 of: WHO 1996. It was conducted

during one week in summer, autumn and winter 2011/2012. The daily household solid waste

generation assessment has been carried out for 150 Libyan families where 947 people in three

main parts of Tripoli city have been chosen randomly. A questionnaire was prepared according to

Buenrostro et al. 2001 and Raje et al. 2001 using door-to-door surveying. The result showed that

the average of total generation quantity, daily generation rate, total volume and density were

1415 kg, 0.64 kg/person/day, 19.3 m3 and 74.4 kg/m3 respectively in Tripoli city. Household solid

waste contains 36.3% organic matter and 32.5% recyclable materials (glass, paper, plastic, met-

als). The total generation quantity, daily generation rate, total volume and density were in Tripoli

city agreed with those for African and Arabic countries. But the problem is that Tripoli suffers

from insufficient municipal solid waste management and lack of sanitary landfills

In this study, the solid and liquid wastes from the olive oil processing industry were evaluated as substrates for Yarrowia lipolytica growth with the aim of lipase production. Olive mill wastewater and olive oil cake seemed to provide the necessary nutrients and physical support for yeast growth and enzyme production. The highest lipolytic activity of 850 IU dm(3) was achieved after 4 days of submerged cultivation in supplemented olive mill wastewater. In addition, olive oil cake appeared to be a convenient substrate for lipase production under a solid-state fermentation mode. Lipase production was further improved by media supplementation and/or change in the physical settings of the experiment. However, the most significant improvement of lipase production under solid-state fermentation was achieved by an alkaline treatment of the substrate (more than 10-fold), when the amount of produced lipase reached up to approximate to 40 IU g(-1) of substrate.

Olive oil cake is a by-product from the olive oil processing industry and can be used for the lipase and protease production by Candida utilis in solid state fermentation. Different carbon and nitrogen sources were evaluated, and the results showed that the supplementation of the substrate with maltose and starch as carbon sources and yeast extract as a nitrogen source significantly increased the lipase production. The best results were obtained with maltose, whereas rather low lipase and protease activities were found with glucose and oleic acid. Response surface methodology and a five-level-three-factor central composite rotatable design were used to evaluate the effects of the initial moisture content, inoculum size and fermentation time on both lipase and protease activity levels. A lipase activity value of ≈25 U g(-1) and a protease activity value of 110 U g(-1) were obtained under the optimized fermentation conditions. An alkaline treatment of the substrate appeared to be efficient, leading to increases of 39% and 133% in the lipase and protease production, respectively. The results showed that the olive cake could be a good source for enzyme production by solid state fermentation.