The present study was set to develop a robust and economic biorefinery process for continuous co-production of ethanol and xylitol from rice straw in a membrane bioreactor. Acid pretreatment, enzymatic hydrolysis, detoxification, yeast strains selection, single and co-culture batch fermentation, and finally continuous co-fermentation were optimized. The combination of diluted acid pretreatment (3.5 %) and enzymatic conversion (1:10 enzyme (63 floating-point unit (FPU)/mL)/biomass ratio) resulted in the maximum sugar yield (81 % conversion). By concentrating the hydrolysates, sugars level increased by threefold while that of furfural reduced by 50 % (0.56 to 0.28 g/L). Combined application of active carbon and resin led to complete removal of furfural, hydroxyl methyl furfural, and acetic acid. The strains Saccharomyces cerevisiae NCIM 3090 with 66.4 g/L ethanol production and Candida tropicalis NCIM 3119 with 9.9 g/L xylitol production were selected. The maximum concentrations of ethanol and xylitol in the single cultures were recorded at 31.5 g/L (0.42 g/g yield) and 26.5 g/L (0.58 g/g yield), respectively. In the batch co-culture system, the ethanol and xylitol productions were 33.4 g/L (0.44 g/g yield) and 25.1 g/L (0.55 g/g yield), respectively. The maximum ethanol and xylitol volumetric productivity values in the batch co-culture system were 65 and 58 % after 25 and 60 h, but were improved in the continuous co-culture mode and reached 80 % (55 g/L) and 68 % (31 g/L) at the dilution rate of 0.03 L per hour, respectively. Hence, the continuous co-production strategy developed in this study could be recommended for producing value-added products from this hugely generated lignocellulosic waste.

In this study, Propionibacterium freudenreichii was used for in situ production of conjugated linoleic acid (CLA) in yogurt. Firstly, effects of process variables, including strain type, percentage of milk fat, percentage of inoculum, quantity of sunflower oil, concentration of inulin, temperature of fermentation and time of storage at 4°C, on production of CLA by Propionibacterium freudenreichii were investigated using screening method of the Plackett–Burman design. Then optimisation of CLA production process was conducted using three major factors of milk fat percentage, inulin concentration and storage time at 4°C using central composite design. Analysis of variance established that the models were highly significant (P ? 0.05). The model demonstrated that the production of CLA was affected by these three factors. Optimised CLA production by Propionibacterium freudenreichii ssp. shermanii in yogurts was achieved after 17 days of storage at 4°C in skim-milk containing 1.75% (w/w) fat and 2.25% (w/v) inulin as prebiotic. Reconfirmation test established that at the highlighted optimum conditions, the highest concentration of produced CLA was 6.4 mg g–1 lipid in yogurt, which is a 256% increase in total CLA production, compared with control samples. Results demonstrated that Propionibacterium freudenreichii ssp. shermanii not only leads to production of synbiotic yogurts containing inulin but also increases CLA production in yogurts.

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