Ethanol has been known for a long time, being perhaps the oldest product obtained through traditional biotechnology. It is an attractive, sustainable energy source for fuel additives. Based on a four-level central composite design (CCD) involving the variables substrate composition (20-100%) X 1 , pH (4.5-6.5) X 2 , incubation temperature (28 -36 C) X 3 , and fermentation time (12-60 h) X 4 , a response surface methodology (RSM) for the production of ethanol using waste cashew apple juice as substrate by Zymomonas mobilis MTCC 090 was standardized. The design contains a total of 31 experimental trials with the first 16 organized in a fractional factorial design and 25 to 31 involving the replications of the central points. Data obtained from RSM on ethanol production were subjected to the analysis of variance (ANOVA) and analyzed using a second-order polynomial equation, which resulted in the optimized process conditions of 62% (v=v) as substrate concentration, pH of 5.5, temperature of 32 C, and fermentation time of 37 h. Maximum ethanol concentration (12.64 g=L) was obtained at the optimized conditions in an anaerobic batch fermentation.

Ethanol production from agricultural products mainly corn, wheat, sweat potato and residue are gaining importance and requires an industrially viable novel technology namely simultaneous saccharification and fermentation process. This process has an advantage of carrying out saccharification using enzyme and fermentation using yeast in a single fermenter. The investment cost for industrial ethanol production using cheap agricultural residues can be well achieved using SSF process. The success of SSF process greatly depends upon the pretreatment methods using different enzymes to break the complex carbohydrates to simple sugars. Optimization of key process variables is essential to maximize the ethanol yield from suitable substrates. The key process variables affecting the SSF process are pH, temperature, fermentation time, enzyme concentration and substrate concentration. The medium components are to be screened for effective nitrogen, potassium and phosphorous sources to increase the ethanol yield.

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The usage of agricultural wastes for enzymes production is considered an essential part in any approach to accomplish goals to reduce environmental pollution and disposal of waste. In the present investigation, xylanase enzyme production by Aspergillus fumigatus using agro-industrial waste sugarcane bagasse with solid state fermentation was studied by keeping the best possible values of process variables, substrate concentration, temperature, incubation time, initial moisture content, and initial pH of the medium. The above-mentioned variables affecting the fermentation conditions were optimized using response surface methodology (RSM). To estimate individual and interaction effects, the central composite design was used. The most favorable process variables attained were substrate concentration = 9.88 g, temperature = 35.73°C, incubation time = 120.05 hours, initial moisture content = 71.30%, and initial pH = 4.98. From analysis of variance, an R 2 -value of 0.9848 signifies a good agreement between the experimental and predicted values for sugarcane bagasse. Also, the fitness of the model is confirmed by a high R 2 -value. The RSM shows that xylanase activity of 417.521 IU/gds was achieved for the optimized process environment. In addition to xylanase activity, a poor quantity of carboxy methyl cellulase activity was also recorded. This study is carried out for cost-effective xylanase production by using agro-industrial waste as cheaper carbon source. It can reduce environment pollution and also minimizes the cost for disposal of industrial waste.