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The production of xanthan gum, an industrially important microbial exopolysaccharide, was enhanced by using Xanthomonas campestris cells adsorbed to cotton fibers. However, the function of xanthan polymers during cell adsorption has not been elucidated. Polyethylenimine (PEI), a cationic polyelectrolyte, was employed to investigate respective effects of fiber surface properties and xanthan polymers during cell adsorption. Adsorption of X. campestris cells to fiber was independent of fiber roughness and hairiness, and the effect of electrostatic interactions between cells and fiber was insignificant. Fiber hydrophilicity was critical in initiating cell-fiber contacts, whereas xanthan polymers enhanced retention of cells on fiber surface. The untreated cotton showed the highest immobilization efficiency and xanthan production.

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Growth stimulating effects of LYCH leaf hydrolysates on Pediococcus acidilactici IMT101 cells were observed when MRS broth was supplemented with 20% (v/v) H1+H2, the mixture of hydrolysates prepared by a traditional tea-making process. Cells grown on MRS containing H1+H2 showed a shortened lag phase while yielding a cell concentration (X(s)) significantly higher than other conditions investigated entering stationary phase. The maximal specific growth rate (mu(max)) was also the highest among all. Microwave-assisted extraction (MAE) at 80 degrees C for 2h (M80(2h)) released more amino acids but less sugar (fructose, glucose, and sucrose) than in H1+H2. Both X(s) and mu(max) reached in M80(2h)-supplemented MRS broth were lower than those in MRS containing H1+H2. No correlations between amino acids and cell growth were found. P. acidilactici cells grown in MRS broth in general showed higher consumption of carbohydrate in comparison with those in M17 broth containing the same carbohydrate. In the absence of FOS, the increased glucose concentration in MRS when supplemented by H1+H2 hydrolysates appeared to be responsible for the stimulatory effects on P. acidilactici growth. The growth-enhancing effects of LYCH leaf hydrolysates indicate the potential of developing new applications for LYCH leaves in promoting the growth of other probiotic cells using a simple process.

Syneresis remains the most challenging drawback of cooked rice if not consumed within a couple hours of preparation for household, restaurants and food processors. Microbial polysaccharides xanthan and curdlan were employed to assess their feasibility as a coating agent to prevent syneresis after cooking and during storage. The curdlan solution at 0.02% was found the most ideal coating agent that could be added to the broth when cooking rice with an automatic rice cooker. The ability of curdlan to form a two-dimensional sheet-like structure was desirable in helping to retain the moisture of cooked rice for up to 4 days without noticeable changes in texture and color. Xanthan and curdlan mixtures provided cooked rice additional gel-like texture, which could be desirable when chewy rice is preferred. PRACTICAL APPLICATIONThe ability of curdlan to reduce syneresis of cooked rice is highly applicable as a tool to prevent moisture loss of rice and subsequently extend the storage time of cooked rice. Such a tool should find applications not only for restaurants that constantly have excessive rice, but also for processed food that struggles with syneresis during processing and storage. The present research demonstrated that dilute solutions of microbial polysaccharides such as xanthan and curdlan could be used as a coating agent to improve the quality attributes (texture, color, etc.) of foods.