生物加工与生物技术杂志

This study was carried out to analyze the garification process using Artificial Neural Network (ANN) based model of steady state simultaneous heat and mass transfer. Convective heat and mass transfer coefficients were obtained during garification process of fermented mash from cassava ages of different maturity. Empirical equations developed for heat, (hc) and mass, (hm) transfer coefficients [hc=0.017t2-0.388t+3.039, hm=0.042t2-0.914t+5.481]; with (R2>0.9) were best described by polynomial relationships. The optimum ANN model that produced convective heat and mass transfer coefficients for the garification process consisted of two hidden layers and twenty-five neurons in each hidden layer, with mean square error, mean absolute error, sum square error and R2 of 0.000015, 0.0030, 0.0082% and 0.995, respectively. The developed ANN model can be useful in the determination of heat and mass transfer rate for garification process and wide range of physical conditions. These results are equally important considerations for obtaining quality gari for commercial production.

The aim of our work is to compare the performances and the quality of treated water of a Tunisian textile industry through a conventional activated sludge (CAS) and a membrane bioreactor (MBR). During the first period, CAS and MBR1 worked under similar biological conditions (MLSS of 4-6 g.L-1). MBR showed a better global efficiency. Permeate of MBR was always free from TSS and turbidity whereas CAS treated water contained TSS and turbidity varying respectively between 0 and 0.13 g.L-1 and 10 and 20 NTU. If colour and soluble COD removal efficiency was closed (95% and 97%), it appeared necessary to add coagulant in the CAS to insure an adequate sludge settling and complete the colour removal. During the second period, the sludge retention time was increased in the MBR2 in order to reach 8-10 g.L-1 of suspended solids. The COD effluent value was further reduced (MBR2: 50 mg.L-1, MBR1 150 mg.L-1 and CAS 180 mg.L-1). The SRT allows a reduction of 20% of the sludge production but this effect was counterbalance by rheological sludge properties. Furthermore, the MBR has shown great aptitude to withstand high loading rate variations and to product a constant quality effluent.

In biological reactors, isolation of unwanted microorganisms by using sterilization is essential. One of the important reasons of microbial contamination in industrial fermenter is bioreactor poor design which causes to create dead spot during sterilization. Therefore, identifying the dead spots in the sterilization process is crucial which could be accomplished by computational fluid dynamics (CFD). In this study, for identifying the spots which their thermal distributions are not uniform (due to fermenter geometry deficiency), the sterilization process in a 140 m3 fermenter (without culture media) were modeled (129-133°C and 15 min). Study of temperature profile, velocity and stream lines shows that in the manhole, around the coils, steam inputs and below the impeller on the agitator shaft are the places that the risk of dead spot creation is high.

In this study, Alliinase extracted and purified from shallots was comprehensively examined. Its molecular weight was determined as 50 kDa, and its optimal working conditions were identified as pH 8 and 40ºC. Its activity was significantly and positively affected by the metals K+, Na+, Ga2+, Mg2+ and Fe2+. Purified Alliinase was immobilized by alginate and the optimized conditions for this process were: a sodium alginate concentration of 2.5%, a CaCl2 concentration of 4.0%, a Glutaraldehyde concentration of 0.75%, and a ratio of sodium alginate solution and Alliinase solution (by volumn) of 4:3. The ability for free Alliinase and immobilized Alliinase to release flavours from shallots was compared. It was found that immobilization did not compromise Alliinase’s flavor releasing ability. They both released 36 flavouring chemicals from the flavouring precursor, with a similar ratio. This study provided fundamental information for further commercial development of Alliinase produced from shallots.

Antrodia cinnamomea is a well-known medicinal mushroom producing potent bioactive triterpenoids; it only grows in Taiwan. Its anti-tumor activity remains the focus of current research on triterpenoids. However, a main drawback of producing mycelia by submerged cultures is the rather low levels of triterpenoid produced. In this research, different kinds of Chinese herb water extracts were added into the media to study their effects on the formation of triterpenoids of A. cinnamomea in the thin stillage submerged cultures. Astragalus water extract was the most effective for enhancing triterpenoids production. With an addition of Astragalus water extract of 2% (v/v), the content and concentration of triterpenoids were 10.36 mg/g DW and 85.28 mg/L, respectively, which were 3-fold and 5-fold higher than the control, respectively, on the 21th day. The results reveal that although the addition of Chinese herb water extract lengthens the exponential phase and reduces the specific growth rate, the production rate of biomass, intracellular polysaccharide (IPS) and triterpenoids were still significantly enhanced. Moreover, this study also demonstrates the feasibility of reusing thin stillage for the mycelia culture of A. cinnamomea.