The main objective of this study was to evaluate the effect of yeast immobilization on ethanolic fermentation of very high gravity (VHG) medium and to determine the concentrations of yeast storage carbohydrates like trehalose and glycogen during the process. Repeated batch ethanolic fermentation of VHG medium was carried out using Saccharomyces cerevisiae immobilized separately within Ca-alginate and κ-carrageenan polymers. Immobilization yields (Y I ) were between 80 and 90% and ethanol yields (Y P/S ) were more than 0.41 with both carriers. An average fermentation efficiency of nearly 70% was observed in 48-h fermentation batches. Compared to free cells, a reduction of more than 50% in the accumulated trehalose, and a twofold increase in intracellular glycogen levels were observed in immobilized yeast cells at 24 and 48 h of fermentation, respectively, with both carriers. The increased viability (up to four-fold higher) upon 18% ethanol treatment for 2 h, and the sustained viability over four successive batches of immobilized cells showed the protective nature of the polymer carriers. The chemical nature of the carriers was not found to have any adverse effect on ethanol yields. Application of immobilized yeast in porous matrices may serve as a feasible and better technique for ethanol production, at both pilot and industrial scale.

Optimization of media and submerged fermentation conditions using central composite design for increased endoglucanase production by Cladosporium sp. NCIM 901 [Cladosporium sp. NCIM 901 ile artmış endoglukanaz üretiminin merkezi kompozit düzenleme kullanılarak vasat ve dipüstü fermentasyon durumunun optimizasyonu]*

The aim of this study was to optimize the supplementation of custard apple, pomegranate peel along with KH2PO4, (NH4)2SO4 and MgSO4 for maximum endoxylanase production by Trichoderma koeningi isolate on pretreated corn cobs using CCD. Predicted endoxylanase yield was highest (3242.43 U/g) with the actual yield of (3107.58U/g) from 2% NaOH pretreated corn cobs. The model predicted R2 value of 0.9147% indicating that it was appropriate to predict the levels of variables to achieve maximum endoxylanase yield. The produced endoxylanase clarified mango juice of Baneshan and Totapuri varieties at 40°C and 56 h. The endoxylanase treatment enhanced the clarity of Baneshan juice by 51.7% with a release of 121.1 mg/ml of reducing sugars at an optimized enzyme dose of 9.6 U that led to maximum flow rate of 8 ml/min. In the case of Totapuri juice, there was 43.4% increase in clarity and release of 102.6 mg/ml reducing sugars at an optimized enzyme dose of 12.8 U that lead to a maximum juice flow rate of 6 ml/min. The HPLC analysis showed that the hydrolysed products of mango juice were xylose and xylo-oligosacharides. An optimized xylanase production was achieved from low cost agro residues, which results in the reduction of enzyme cost.

The current experiment aimed to find the ideal pretreatment process parameters for maximize the yields of cellulose, fermentable simple sugars, and ethanol from bagasse that had successfully treated with hydrogen peroxide (H2O2). The pretreatment process variables like substrate concentration, H2O2 concentration, pretreatment time, and temperature were studied individually and in combination to see how they affected the response variables like cellulose, hemicellulose, and lignin content in the pretreated pulp. This was done using the response surface methodology (RSM). The best pretreatment conditions for sugar cane bagasse were found through experiments using a factorial central composite design (CCD). The highest cellulose and hemicellulose yields, which were determined by RSM to be 69.3% and 76.4%, respectively, with a lesser lignin yield (4.8%), were achieved at a substrate concentration of 2%, an H2O2 loading of 20%, a temperature of 120 oC, and a pretreatment duration of 120 min. The experimental actual and predicted outcomes were well correlated, demonstrating that the model may be applied to effectively pretreat lignocellulosic biomass. The model has been validated when there is no difference between experimental actual values and anticipated values. The modifications in the chemical structure of bagasse during pretreatment was analyzed using FTIR. Comparatively, samples processed with H2O2 had a higher crystallinity (CI = 23.63%) than untreated bagasse (CI = 15.84%). The loss of lignin, which contributed the greatest CrI, increased the proportion of cellulose in treated bagasse compared to untreated bagasse. The bagasse that had a H2O2 concentration pretreatment showed the highest reducing sugar yield (58.7 mg/g). Pretreated bagasse had a higher ethanol output (73.88 g/L) than untreated bagasse (45.49 g/L).