Low-cost raw materials can be used to reduce significantly the production cost of polyhydroxyalkanoates (PHA). In this study, extruded rice bran (ERB) and extruded cornstarch (ECS) were used as carbon sources to produce PHA by an archaea, Haloferax mediterranei, which cannot use native rice bran or cornstarch as a carbon source. By employing pH-stat control strategy to maintain pH at 6.9-7.1 in a 5-liter jar fermentor using ERB:ECS (1:8 g/g) as the major carbon source, we obtained a cell concentration of 140 g/L, PHA concentration of 77.8 g/L and PHA content of 55.6 wt.% in a repeated fed-batch fermentation. In contrast, when ECS was used as the major carbon source, we obtained 62.6 g/L cell concentration, 24.2 g/L PHA concentration and 38.7 wt.% PHA content. Under a hyper-saline condition and with no nitrogen-limitation restriction, the repeated fed-batch process can be sustained a long time for the mass production of PHA.

Of three beta-galactosidases from Aspergillus oryzae, Kluyveromyces lactis and Bacillus sp., used for the production of low-content galacto- oligosaccharides (GOS) from lactose, the latter produced the highest yield of trisaccharides and tetrasaccharides. GOS production was enhanced by mixing beta-galactosidase glucose oxidase. The low-content GOS syrups, produced either by beta-galactosidase alone or by the mixed enzyme system, were subjected to the fermentation by Kluyveromyces marxianus, whereby glucose, galactose, lactose and other disaccharides were depleted, resulting in up to 97% and 98% on a dry weight basis of high-content GOS with the yields of 31% and 32%, respectively.

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A beta-fructofuranosidase (EC 3.2.1.26) was purified to homogeneity from Aspergillus japonicus TIT-KJ1. The enzyme had an optimum pH for activity of 5.4 and pH stability at 7.0-8.4. The optimum temperature at pH 5.4 was 60 degrees C. The enzyme had a molecular weight of 236,000 with two subunits and an isoelectric point of pH 4.0. The enzyme was inactivated by 5 mM Hg2+ and Ag+. The enzyme had a high transfructosylating activity. Treatment of 50% (w/v) sucrose with the enzyme under optimum conditions afforded more than 55% fructooligosaccharides.

beta-Fructofuranosidases from Aspergillus niger ATCC 20611 and Aspergillus japonicus TIT-KJ1 were purified and immobilized covalently onto methacrylamide-based polymeric beads. The porous, oxriane-containing support was reactive and could bind enzymes in a buffered solution at room temperature with a density up to 0.4 mg of protein g-1 of support with 100% immobilized yield. Neither the optimum temperature for the highest enzymatic activities nor the batch reaction pattern for fructooligosaccharides formation catalyzed by beta-fructofuranosidases was changed by immobilization. The amount of fructooligosaccharides produced from 50% (w/w) sucrose solution using the prepared immobilized enzymes was determined to be approximately 60% of the total sugars in the reaction mixtures. This level of fructooligosaccharides produced by the immobilized enzymes was comparable to that resulting from processes employing other immobilized biocatalysts as shown in the literature. The fraction of total fructooligosaccharides presented in the final mixture increased with the initial sucrose concentration, while fractions of glucose and fructose decreased with an increase sucrose concentration.