Highly efficient fermentation of 5-keto-D-fructose with Gluconobacter oxydans at different scales.

BACKGROUND: The global market for sweeteners is increasing, and the food industry is constantly looking for new low-caloric sweeteners. The natural sweetener 5-keto-D-fructose is one such candidate. 5-Keto-D-fructose has a similar sweet taste quality as fructose. Developing a highly efficient 5-keto-D-fructose production process is key to being competitive with established sweeteners. Hence, the 5-keto-D-fructose production process was optimised regarding titre, yield, and productivity. RESULTS: For production of 5-keto-D-fructose with G. oxydans 621H ΔhsdR pBBR1-p264-fdhSCL-ST an extended-batch fermentation was conducted. During fructose feeding, a decreasing respiratory activity occurred, despite sufficient carbon supply. Oxygen and second substrate limitation could be excluded as reasons for the decreasing respiration. It was demonstrated that a short period of oxygen limitation has no significant influence on 5-keto-D-fructose production, showing the robustness of this process. Increasing the medium concentration increased initial biomass formation. Applying a fructose feeding solution with a concentration of approx. 1200 g/L, a titre of 545 g/L 5-keto-D-fructose was reached. The yield was with 0.98 g5-keto-d-fructose/gfructose close to the theoretical maximum. A 1200 g/L fructose solution has a viscosity of 450 mPa∙s at a temperature of 55 °C. Hence, the solution itself and the whole peripheral feeding system need to be heated, to apply such a highly concentrated feeding solution. Thermal treatment of highly concentrated fructose solutions led to the formation of 5-hydroxymethylfurfural, which inhibited the 5-keto-D-fructose production. Therefore, fructose solutions were only heated to about 100 °C for approx. 10 min. An alternative feeding strategy was investigated using solid fructose cubes, reaching the highest productivities above 10 g5-keto-d-fructose/L/h during feeding. Moreover, the scale-up of the 5-keto-D-fructose production to a 150 L pressurised fermenter was successfully demonstrated using liquid fructose solutions (745 g/L). CONCLUSION: We optimised the 5-keto-D-fructose production process and successfully increased titre, yield and productivity. By using solid fructose, we presented a second feeding strategy, which can be of great interest for further scale-up experiments. A first scale-up of this process was performed, showing the possibility for an industrial production of 5-keto-D-fructose.

Outpatient rehabilitation of workers with musculoskeletal disorders using structured workplace description.

OBJECTIVES: In most industrialized countries musculoskeletal disorders contribute considerably (25%) to illness induced work absence. A special interest to reduce worker absences exists in highly specialized industries such as jet manufacturing, where specific knowledge is hard to replace. We investigated the reduction and sustainability in sick leave days by a workplace oriented outpatient rehabilitation program based on structured information exchange between occupational physicians and therapists. METHODS: Sick leave days reduction and return-to-work-ratios were analysed for 79 male blue collar workers with musculoskeletal disease, who voluntarily participated in an outpatient rehabilitation treatment between 2002 and 2005. During rehabilitation therapy standardized workplace descriptions were given to the therapists and individual return-to-work (rtw) schemes were implemented. Therapy lasted from 3 to 4 weeks followed by workplace reintegration. Off-work-time was calculated from 0 to 6 years before and 0 to 3 years after rehabilitation from insurance and industrial medical reports. RESULTS: A total of 97% of the patients returned to their original job at the workplace, usually directly after the rehabilitation. Average sick leave days per year were reduced from 48.8 +/- 32.8 days before to 34.2 +/- 37.3 days after the rehabilitation. The therapy interrupted an increase in sick leave days over the years stabilizing absence at a low level for at least 2 years. Duration of illness related work absence was the only significant predictor for sick leave reduction (P < 0.05). Other common risk factors for musculoskeletal diseases like smoking or body mass index did not significantly influence the therapeutic effect. CONCLUSIONS: Our results support evidence that information exchange for workplace description and rehabilitation therapist may help to reduce sick leave days and achieve very high rtw-ratio. However it is important to observe the effects of this shared information for longer intervals.