Batch and continuous fermentation of lactic acid by Lactococcus Lactis using sago starch hydrolysate
Sago starch was hydrolysed enzymatically for use in both the batch and continuous fermentation studies. The best parameters for enzymatic hydrolysis were obtained from a glucose concentration of 20% DS sago starch, liquefaction and saccharification at pH 6.5 and pH 4.5 respectively, with the incubat...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2002
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| Subjects: | |
| Online Access: | http://ir.unimas.my/id/eprint/37998/1/Paula%40Paulawati%20Jolhery%20ft.pdf |
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| Summary: | Sago starch was hydrolysed enzymatically for use in both the batch and continuous fermentation studies. The best parameters for enzymatic hydrolysis were obtained from a glucose concentration of 20% DS sago starch, liquefaction and saccharification at pH 6.5 and pH 4.5 respectively, with the incubation period for liquefaction at 2 hours. Optimum enzyme
concentration for hydrolysis were 0.5μl/g and 0 6μl/g for Termamyl 120L and Dextrozyme, respectively. Batch fermentation trials utilising different initial glucose concentration of either 60g11 or 70g/1 exhibited only minimal differences in the amount of lactate and biomass produced kligher initial glucose concentration results in higher residual glucose, thus needed
longer i riod for complete consumption. Batch fermentation trials under controlled pH (pH6) induced faster with almost complete glucose consumption (98% consumption, residual
glucose 1. lOg/l) compared to uncontrolled pH (75.8% consumption, residual glucose 13.4g/I) after 48 hours. The other advantage is the higher lactate production (37.3g/l
compared to 30.7g/l) and volumetric lactate productivity (0 78g/Ihr compared to 0.64g/Ihr). Continous fermentation trials were analysed and limited to dilution rates of 0.05hr1, 0.06hr'
and 0.08hr' where lactate concentration was reduced gradually from 37. lg/1 to 34.4g/l and to 30.3g11, respectively. Biomass (DCW) was highest at the lowest dilution rate of 0.05hr', at
2.11g/1. This decreases at higher dilution rates of 0.06"' and 0.08hr' to 1.97g/l and 1.83g/l, respectively. As such, higher dilution rates were not feasible due to possible wash-out of
viable cells from the fermemor. Apart from the decreasing concentration of the biomass, high dilution rate (0.08hr"') also suffers from uneconomically high concentration of residual
glucose (22.2g/1). In order to maintain high cell density in the fermentation while working at higher dilution rate (thus increasing lactate productivity), a hollow fibre filter module (HFM) was introduced into the system, at dilution rates 0.1 lhr', 0.24hr' and 0.33hr-', resulting in higher lactate concentrations at 41 Og/l, 38.4g/1 and 35.4g/l, respectively. Consequently, volumetric lactate production was highly amplified at 4.51 g/l, 9 22g/1 and 1 1.70g/l while
maintaining high cell density in the fermentor at 2.87g/l, 3.35g/l and 3.60g/l, respectively. The high cell concentration at high dilution rate managed to reduce the concentration of residual glucose while generating higher lactate production in the system |
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