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In order to elucidate the hybridoma life cycle and the limiting factors in perfusion systems, we performed cultures in a stirred tank bioreactor, coupled to an external tangential flow filtration unit. Cell density and antibody production in perfusion were consistent with previous studies. The average life span of the cells (2.1-2.2 days), antibody, productivity per cell produced (30-38 mg/10(9) cells) and cell size diameter evolution appeared similar to values observed in batch cultures. These observations highly suggest a similar "grow or die" life cycle. Cell and antibody production, strictly related to the medium perfusion rate, seem to be under the control of the nutrient availability. A hypothesis to explain such a life cycle of hybridoma cells in perfusion systems and a model for viable and dead cell density is proposed.

Fish peptones from tuna, cod, salmon, and unspecified fish were compared with a casein one by using a new method based on Gompertz modeling of microbial growth. Cumulative results obtained from six species of bacteria, yeasts, and fungi showed that, in most cases, these fish peptones are very effective. Nevertheless, this study raised some questions about the standardization of fish raw material, the enzymatic hydrolysis of fish proteins, and the composition of the culture medium used for testing the peptones.

The effects of the herbicide Roundup® (glyphosate) on natural marine microbial communities were assessed in a 7 day field experiment using microcosms. Bottles were maintained underwater at 6 m depth, and 10% of their water content was changed every other day.The comparison of control microcosms and surrounding surface water showed that the microcosm system tested here can be considered as representative of the natural surrounding environment. A Temporal Temperature Gradient gel Electrophoresis (TTGE) was run on 16S This study demonstrates that a disturbance was caused to the marine microbial community exposed to 1 µg L -1 Roundup concentration, a value typical of those reported in coastal waters during a run-off event.