Thesis Abstract

Abstract
The production of lipase by microorganisms has gained significant attention due to its industrial applications. In this study, a strain of Micrococcus sp. isolated from the environment was found to exhibit high lipase activity. The aim of this research was to optimize the culture conditions for maximum lipase production by this isolated Micrococcus strain. The effects of various culture parameters such as temperature, pH, carbon source, nitrogen source, and agitation rate on lipase production were investigated using a one-factor-at-a-time approach. The results indicated that the optimal temperature for lipase production was 30°C, with a slight decrease in activity observed at higher temperatures. The pH range of 7.0-8.0 was found to be suitable for maximum lipase production, with acidic or alkaline conditions leading to reduced enzyme activity. Different carbon sources were tested, with olive oil showing the highest lipase production, followed by tributyrin and glucose. Among the nitrogen sources evaluated, peptone was found to significantly enhance lipase production compared to other sources such as ammonium sulfate and yeast extract. Additionally, the agitation rate of 150 rpm was determined to be the most favorable for lipase production by the isolated Micrococcus strain. Furthermore, the production of lipase by the isolated Micrococcus strain was found to be inducible, with the addition of olive oil resulting in a significant increase in enzyme activity. The time course study revealed that maximum lipase production occurred during the late log phase of growth, highlighting the importance of monitoring the growth phase for optimal enzyme production. Overall, this study provides valuable insights into the culture conditions required for maximizing lipase production by an isolated strain of Micrococcus. The findings suggest that maintaining a temperature of 30°C, pH 7.0-8.0, utilizing olive oil as a carbon source, peptone as a nitrogen source, and an agitation rate of 150 rpm could significantly enhance lipase production. Understanding and optimizing these culture conditions can contribute to the development of efficient bioprocesses for industrial lipase production using Micrococcus sp.

Thesis Overview

1.0   INTRODUCTION

Ugba also called ukpaka is a popular food delicacy in Nigeria especially among Ibo ethnic group. It is rich in protein and is obtained by a solid state fermentation of the seed of African oil bean tree (Pentaclethra macrophyllaBenth). It is essential food item from various traditional ceremonies where it is mixed with slices of boiled stock fish (ugba and okpoloko). The natural fermentation of the seed which at present is still done at the house-hold level, renders the production nutritious, palatable and non-toxic (Enujiugha, 2002).

Its production, like many African fermented foods depends, entirely on mixed fermentation by microorganism from diverse source.

Some of these seeds have been exploited as soup bases such as Gbegiri from Vigna unguicuata (Akanbi, 1992). Others are fermented and used as condiments and seasonings such as okpei from Prosopis africana (Achi, 1992) and ogiri from Ricinus cummunis (Odunka, 1989). Another of such seeds is the African oil bean seed (Pentaclethra macrophylla Benth), a highly nutritious leguminous crop seed abundant in the rain forest areas of west and central Africa.

Pentaclethra macrophylla Benth is a large woody plant abundant in the rain forest areas of west and central Africa. It’s origin in Nigeria is believed to be around 1937 (Ladipo, 1984); where it is found in the South Nigeria, (Mbajunwa et al, 1998).

“Ugba” Pentaclethra macrophylla Benth belongs to the Family Leguminosae and sub-family microsoideae (Keay, 1989 and NFTA, 1995).

Ugba seeds are irregular and oval, they are flat, black and hard pods. It is composed of oil, protein and small amounts of carbohydrate (Obeta, 1982).

Production of Ugba is still on age old traditional family in the rural area. The fermentation depends on random inoculation of boiled slices of the oil bean seed by microorganism within he immediate environment. Earlier report attribute the sources of the micro-organism to the leaves used in packaging, human handling, container and utensils used in processing (Obeta, 1993, Odunfa & Oyeyiola, 1985).

A number of researches have been carried out to know what causes this fermentation, and was attributed to micro-organisms that are probably introduced through the air, water, and banana leaves. Organisms such asMicrococus roseus, Micrococcus luteus, Leuconostoc mesenteroides,Staphylococcus aureus, Staphylococcus epidermidis, Bacillus substilis,Bacillus megaterium and Bacillus circclans, E-Coli

Fermented African oil bean seed (ugba), has a high rate of susceptibility to microbial spoilage and therefore has a very short self life of 1-2 weeks (Enujiugha & Olajundoye, 2001).

Manifestation of food spoilage are many and vary typically resulting in an off smell, colour, taste and texture.

Reports by Mbajunwa (1998) Obeta, (1983) and Nwagu et al. (2010) indicates that micrococcus species do not play an active role during microbial fermentation of Ugba.

However, further work on spoilage association of ugba by Nwagu et al(2010) showed that the population of Micrococcus sp increased with increase in keeping time of ugba. This indicates the ability of micrococcus to thrive in the alkalophilic environment while constituting as a spoilage organism of ugba. This may be attributed to the ability of microorganism to produce lipase, lipase, or protease able to utilize protein, carbohydrate or lipid content of ugba as source of nutrition (Njoku et al., 1990).

Lipase are defined as glycerol ester hydrolases (EC3.1.1.3) hydrolyzing tri-di and mono-glycerides present at oil-water interface (Saxena et al, 1999). Some lipases are also able to catalyze esterification, trans-esterification and enantioselective  hydrolysis reaction (Nine et al, 2001, Shintre et al, 2002). The interest in microbial lipase production has increased in the last decades, because of its large potential in a wide range of industrial applications and additives in food processing (flavour modification).

1.1   Aims and Objectives

This work is aimed at the following;

a.           isolating micrococcus from fermented ugba

b.           producing lipase from the micrococcus from ugba