Variation Of The Medium Composition And The Effects On Growth On Rhizopus Nigricans.

ABSTRACT

Rhizopus nigricans was grown in various mediums with different carbon sources, nitrogen sources and at differing concentrations with all mediums adjusted to pH 5.5; growth was examined and recorded at the end of the experiment. Growth of the mycelial mass appears to caused by the Nitrogen Source, Corn Steep Liquor with it’s addition of miscellaneous trace metals and vitamins.

INTRODUCTION

Rhizopus nigricans is a type of mould that grows on bread and is commonly known as �Bread Mould’ (3). R. nigricans was subjected to varying types of carbon sources, Glucose monohydrate, Molasses, Starch and Lactose and at different concentrations, 2% and 4%. The different Nitrogen sources were Corn Steep Liquor 2.0%, Diammonium Hydrogen Phosphate (NH4)2HPO4 .2% , Urea .1%.

Variation of the media was done to investigate what affects the growth of R. nigricans.

MATERIALS AND METHODS

Mediums: 12 Mediums were prepared as shown in Table 1, labeled A-L with varying concentrations of Carbon Source and Nitrogen Source. (Table 1). Mediums were divided into 2 flasks, volumes of 250mL, pH adjusted to 5.5 and then autoclaved at 121Ð'oC for 20 minutes.

Mediums containing starch was brought to boil and pH adjusted to 5.5

Inoculums and Harvesting: 2 x Universal bottles with broken up mycelium in it was used to inoculate each medium A вЂ" L. Another 2 x Universal bottles with mycelium in it was filtered through a Buchner funnel, dried overnight in the vaccum oven overnight and then weighed.

Harvesting and weighing of the mycelium mass from all mediums A вЂ" L. This was done by filtering through a Buchner funnel, dried overnight in the vaccum and then weighed.

Growth type; pellet or diffuse was also noted for each medium.

RESULTS

Table 1: Class results on growth of Media Variation 2008

Medium Carbon Source Nitrogen Source Inoculum Mass (g per bottle - dry) Final Mycelial Mass (g per flask - dry) Nett Mycelial Dry Mass (g per flask) Growth Type * Growth increase (%)

A Glucose monohydrate 2% CSL 2.0% 0.27 0.4 0.13 diffuse 48.14815

B Molasses 4% CSL 0.7 10.7 10 diffuse 1428.571

C Starch 2% CSL 0.4* 2.5 2.1* * 525

D Lactose 2% CSL 0.13 2.1 1.97 pellet 1515.385

E Glucose monohydrate 2% (NH4)2HPO4 0.2% 0.46 0.5 0.04 diffuse 8.695652

F Molasses 4% (NH4)2HPO4 0.1 0.21 0.11 diffuse 110

G Starch 2% (NH4)2HPO4 0.18 0.6 0.42 diffuse 233.3333

H Lactose 2% (NH4)2HPO4 0.04 0.04 0 diffuse 0

I Glucose monohydrate 2% Urea 0.1% 0.34 0.41 0.07 pellet 20.58824

J Molasses 4% Urea 0.1 0.8 0.7 pellet 700

K Starch 2% Urea 0.2 0.38 0.18 pellet 90

L Lactose 2% Urea 0.03 0.05 0.02 pellet 66.66667

*Figure was not reported however it is assumed to be comparable with other CSL medias.

Figure 1. Graph showing increase in growth as a % for all Media’s

Figure 2. Graph showing growth for all mediums using Table 1.

DISCUSSION

The class results for growth were reported in Table 1. medium C’s results were not completely reported with only Final mycelial mass being the only figure stated, however .4g was used for the calculations, which was the rough average of the other CSL media’s.

The carbon sources utilized were Glucose monohydrate, Molasses (Sucrose), Starch and Lactose while the nitrogen sources were Corn Steep Liquor (CSL), Diammonium Hydrogen Phosphate (NH4)2HPO4 and Urea. According to Figure 1, the top 4 highest growths was in Medium B, C, D and J, B, C and D all having the same Nitrogen Source, CSL at 2% concentration.

However Medium J did not exhibit a visible result in Figure 2. but when compared via percentage of mass increase in Figure 1, It is clear that it has grown by a large amount. The Molasses Carbon source may contain vital nutrients promoting growth however Medium F with molasses as a carbon source did not show such a large increase, which may be caused by the diammonium hydrogen phosphate.

Mediums A and E-L all show minor increases in growth this does infer that the Nitrogen Source is the key parameter that affects growth.

One anomaly in results (Figure 2) was with Medium B showing a very large increase in growth