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Effect of Different Media and Growth Conditions on the Production of Yeast Biomass

Hosne Ara Begum
Department of Microbiology, University of Dhaka, Dhaka-1OOO, Bangladesh.

Sirajul Hoque
Department of Soil Science, University of Dhaka, Dhaka-1OOO, Bangladesh.

Naiyyum Choudhury
Department of Microbiology, University of Dhaka, Dhaka-1OOO, Bangladesh.

Md. Majibur Rahman
Department of Microbiology, University of Dhaka, Dhaka-1OOO, Bangladesh.

Abstract/ Executive Summary:

Some selected Saccharomyces cerevistae strains were assessed for their biomass production in glucose and molasses media. It was found that the yeast strain SC-4 produced the highest amount of biomass (9.0 gl^-1) at 30°C in MYMP medium containing 12.5% molasses after 18h of incubation. Production of yeast biomass on different media showed that MYMP medium with 12.5% molasses was the most favourable for yeast growth followed by synthetic medium. molasses medium (molasses alone) and MYGP medium. It was also found that MYMP medium having 2.5% molasses was in terms of sugar utilization with 85% sugar consumed. Although higher concentration of molasses in MYMP medium showed more cell mass but the yield (gig) was much lower as compared to that obtained with 2.5% molasses. It was evident from the kinetic data that MYMP medium containing 2.5% molases can be more economical and cost-effective than other media/combinations used for production of yeast biomass.

Keywords: Yeast Biomass, Substrate concentration, temperature, pH on yeast growth.

Location: Dhaka City, Bangladesh.

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Organic products

Objectives:

To find out a suitable medium for yeast biomass production along with the effect of substrate concentration, temperature and pH on yeast growth.

Methodology:

Chemical analysis of molasses: Molasses purchased from local market of Dhaka city was digested with HN0₃-HCL0₄ mixture in moist condition. The digest was analysed for Fe, Zn, Cu, Ca, Mg, by atomic absorption spectrophotometer. Total nitrogen content was determined by Kjeldahls method. Molasses was found to contain 40% sugar, 33.7% moisture, 33.77% carbon, 1.14% nitrogen, 1.44 mgg^-1 Fe, 0.04 rngg^-1 Zn, 0.05 mgg^-1 Cu, 14.4 mgg^-1 Ca, 5.1 mgg^-1 Mg and 0.75 mgg^-1 P. Microorganisms: Selected strains of Saccharomyces cerevisiae were used for cell mass production. The strains were isolated previously in the laboratory of microbiology department from indigeneous sources. Media for cell mass propagation: a. MYMP (malt extract, yeast extract, molasses and peptone) broth medium. Molasses containing different concentrations of sugar 2.5%, 5.0%, 7.5%, 10.0%, 12.5%, and 25% molasses were used in MYMP medium. b. Synthetic medium: This medium is composed of glucose (100gl^-1) yeast extract (8.5 gl^-1), ammonium chloride (1.32 gl^-1), magnesium sulphate (0.11 gl^-1), calcium chloride (0.06 gl^-1). c. Molasses medium: This medium is composed of molasses only (12.5% molasses). d. MYGP medium : This medium is composed of malt extract (0.3%), yeast extract (0.3%), glucose (1 %) and peptone (0.5%). Determination of yeast biomass: Yeast biomass was determined by dry weight method and plate count method. Determination of total sugar: Total sugar was determined following Phenol- Sulphuric acid method. Study on growth kinetics: For detail analysis of cell yield and sugar utilization, the potential yeast strain, SC-4 was grown in MYMP medium containing different concentration of molasses ranging from 2.5% to 25% and dry weight of cells and amount of total sugar left in the medium were analysed every 6h upto 48h.

Source of Information: Bangladesh J. Microbiol. 12 : (1 & 2), 57-63, 1995

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It was found from the current work that the yeast strain SC-4 can be grown in a wide range of temperature, i.e. 25 - 40°C. However, optimal temperature for cell mass production was found to be 30°C which was consistent with the findings, who obtained maximum cell yields in the range of 20-30°C. In the present study, different media have been containing used for cell mass production. Maximum cell mass was produced in the MYMP medium 12.5% molasses. It was observed that most of the sugar was utilized when MYMP medium containing 2.5% molasses was used as substrate whereas with 12.5% molasses only 63% sugar was practically consumed. Substrate has a direct effect on the growth of mircroorganism. Cell mass production increased with increase in molasses concentration upto 12.5% and then decreased with 25%. But utilization of sugar was maximum (85%) with 2.5% molasses containing 1% sugar in MYMP medium. Low Ks value is desirable because it would minimize or reduce the substrate cost.

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