Production of Lactic Acid from Sugarcane Bagasse
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Date
2019-12
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Addis Ababa University
Abstract
Fossil fuel based plastic raw materials are not renewable which in questioned their sustainability
as well as the plastic products of these raw material is sources of an overwhelming
environmental problem due recalcitrant to degradation. Hence, there is an urgent need toward
bio-based plastics research area particularly poly lactic acid (PLA). This study aimed to produce
Lactic acid which is used as a raw material for bio-based plastic (PLA) by a bacteria Lacto
bacillus plantarum using sugarcane bagasse as a carbon source. The effects of glucose
concentration, time and pH on the lactic acid yield were studied. sugarcane bagasse was
pretreated using dilute sulfuric acid as catalyst and a maximum glucose concentration of
3.755g/L was found at a temperature of 105
C, acid concentration of 2.75% and time of 3hrs.The
fermentation experiments were performed in 250 mL Erlenmeyer flasks as small scale laboratory
fermenter containing 100 mL of hydrolysate supplemented with 5g/L of yeast extract and 10mL
of lacto-bacillus plantarum inoculum. The yield of lactic acid from the fermented broth was
determined using HPLC. Response surface methodology (RSM) approach of Design expert
software of version 11 was used to analyze the effects of glucose concentration (3.755g/L,
3.58.g/L and 3.42g/L), pH (4, 6 and 8) and incubation time (10hrs, 20hrs and 30hrs) on lactic
acid production with their respective ranges keeping the temperature and agitation speed
constant. A three-variable, three-level Box-Behnken design was used to develop a statistical
model to describe the relationship between lactic acid concentration and the chosen independent
variables and to observe their effects on the yield using RSM. The model was statistically
significant (p ˂0.0001), did not show lack of fit (p-value = 0.1141) and The Pred R-Squared of
0.9764 is in reasonable agreement with the Adj R-Squared of 0.9956.From the model regression
equation developed, the linear terms of glucose concentration, pH and time and pure quadratic
term of time as well as interaction of glucose concentration and pH, interaction of glucose
concentration and time, and interaction of pH and time had positive effect on the response yield.
On the other hand pure quadratic terms of glucose concentration and pH had negative effect on
the response yield. The maximum yield of lactic acid of 15.79g/L was found at a higher glucose
concentration of 3.755g/L, at a moderate pH of 6 and at a maximum time of 30hrs.
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Keywords
bagasse, lactic acid, hydrolaysate, bio-plastic, Poly lactic acid