Impact of carbon source on β-cryptoxanthin production by Kocuria marina DAGII: a classical approach

Abstract

Kocuria marina DAGII, a potent β-cryptoxanthin (β-CRX) producer, was previously isolated in our laboratory during routine screening of pigment producing bacteria. In this study, a classical approach of one factor at a time was applied for obtaining the maximum β-CRX yield by Kocuria marina DAGII. Growth kinetics and reducing sugar estimation were also done. The β-CRX production medium consisted of Yeast Extract (10 g/L), Bacteriological Peptone (5 g/L), NaCl (4 g/L), Glucose (0-20 g/L) and Maltose (0-20 g/L) at pH 7.9. Experiments were conducted in batch mode with 1% inoculum at 25˚C and 150 rpm for 5 days. The optimal glucose concentration was quantified by varying its concentration from 0 to 20 g/L in absence of maltose. Gradual increase in β-CRX yield was observed up to 7.5 g/L (3.6 mg/L). Beyond this concentration, β-CRX yield was almost constant. Simultaneously, optimal maltose concentration was determined by varying the concentration in range of 0-20 g/L in absence of glucose. Highest β-CRX production (3.25 mg/L) was observed at 10 g/L. Concentrations higher than 10 g/L were inhibitory, suggesting substrate inhibition of β-CRX by maltose. Validation experiment was conducted with Glucose and Maltose fixed at 7.5 g/L and 10 g/L, respectively. Significant increase in β-CRX yield (4.49 mg/L) was observed at 56 h of incubation with 60% utilization of reducing sugar. The bacterium exhibited regular growth pattern in all the experimental set ups. Monod’s model described the bacterial growth with maximum specific growth rate (μmax) of 0.2500 h-1 and 0.2024 h-1 for glucose and maltose, respectively. This suggests that bacterial growth is more influenced by glucose than maltose. However, for maximal β-CRX production, both the carbon substrates are essential.