Background: In recent times, agricultural waste has been utilized in many industries as an energy source in several processes. Wheat straw, one of the most cost-effective raw material, has a great potential to be utilized as a substrate in fermentation to produce lactic acid. Utilization of agro waste material as the carbon source provides a cheap and environment friendly production of lactic acid.
Methods: A comparison of chemical and biological pretreatment of wheat straw and the use of pretreated wheat straw hydrolysate in fermentation of Lactobacillus was carried out using optimized process parameters of temperature and ph. Pretreatment methods using dilute acid and white rot fungus Coriolis versicolor were performed on wheat straw as well as the effect of co-pretreatment with calcium hydroxide on differentially pretreated wheat straw was studied by analyzing sugar and lactic acid concentrations during fermentation. The effect of different pH (7, 8, and 9) on fermentation using dilute acid pretreated wheat straw was observed to lower the lactic production with the increase in ph. Dilute acid pretreatment of wheat straw provided the highest concentration of glucose at 57.2mg/L and subsequently enhanced yield of lactic acid during fermentation while the biologically pretreated wheat straw hydrolysate provided comparatively lower concentration of glucose at 49.2mg/L and thus decreased lactic acid production.
Result: The final lactic acid concentration of 48.14 mg/L was obtained in dilute acid pretreated wheat straw with Yp/s of 0.915 mg/mg, while the use of biologically pretreated wheat straw hydrolysate provided 39.56 mg/L concentration of lactic acid and an Yp/s of 0.908 mg/mg. However, a reduced lactic acid concentration of 27.03 mg/L and 20.62 mg/L was seen after the co-pretreatment of both dilute acid and fungal pretreated wheat straw with calcium hydroxide respectively, indicating its adverse effects on fermentation process.
Conclusion: Pretreatment of wheat straw with dilute acid can be considered a good saccharification method to obtain the optimum concentration of lactic acid in microbial fermentation carried out at optimum temperature and pH conditions.