Fermentors filling

Carbon dioxide is used to increase the natural CO2 content of the beer and as counterpressure in tanks and filling machines. It must be free of water and any aroma. The consumption is 0—10 g/L of beer produced. In major breweries, carbon dioxide is bought in bulk, and in many breweries it is common practice to coUect the surplus CO2 from the fermentors to clean, dehumidify, and compress in a local CO2 plant which is easily automated. 

True. Batch cultures give lower overall outputs than continuous cultures, as they suffer from non-productive down-time (the time taken to empty, clean, re-sterilise and re-fill the fermentor). After inoculation, considerable time can be taken for biomass to build up to a level where substrates are effectively utilised. Continuous cultures do not suffer such drawbacks once they are in operation. 

Postfermentation Care. For white wine, it is considered a good general rule that the less handling the better. Some fill the fermentor full as soon as primary fermentation is finished, leaving the wine on the lees at moderate temperature to make sure that malo-lactic fermentation can be finished swiftly. Others rack immediately but do not add S02 at this point, unless they wish to avoid the malo-lactic fermentation for some reason. It is rare that a H2S problem occurs if wine is left on the lees awhile because elemental sulfur is not much used in eastern vineyards for spraying or dusting, as it is in California. Should it develop, as it does occasionally, the wine is racked immediately in the presence of air and sometimes with the addition of a small dose of copper sulfate. The copper combines with the sulfide to produce an insoluble precipitate. A maximum addition of 0.5 mg/L of copper sulfate is permitted under Federal regulations. 

The first step in the process is gasification of wood followed by conditioning and cleaning of the synthesis gas to give a mixture rich in CO and H2. The synthesis gas is sparged into a broth-filled tank fermentor where bacteria Clostridium ljungdahlii, for example) convert CO and CO2 to ethanol via the following two reactions ... 

In a third paper Scragg et al. (625) compared three different modes of bioreactor operation batch, fed-batch, and draw-fill. The experiments were conducted using airlift fermentors of 7 and 30 liters working volume. Batch and fed-batch cultures were also performed in shake flasks. It appeared that serpentine production in batch cultures in shake flasks was highest. Batch cultures performed in airlift bioreactors showed a lower productivity. Fed-batch cultures showed a lower productivity compared with batch cultures, both in shake flasks and in airlift reactors. When the draw-fill method was used, serpentine production was negligible. 

In batch techniques, the fermentor is filled with medium and inoculated the cells multiply and synthesize the product, simultaneously consuming the nutrients in the medium. At the appropriate time, the culture is drained off and processed. Discontinuous processes are used, e.g. in the production of antibiotics and certain amino acids, which are synthesized only during particular growth phases of the organism. Their discontinuity of operation makes them less suitable for industrial production than continuous processes. 

Steel, particularly stainless steel, is the material most often used today for manufacturing fermentors. Two categories of stainless steel exist one contains molybdenum the other does not. Chrome-nickel-molybdenum steel is more resistant to corrosion and it is necessary for the long-term conservation of sulfited white wines, especially in partially filled tanks in the humid atmosphere above the wine, sulfur dioxide gas is concentrated and the condensation formed on the tank walls is corrosive. For red winemaking and storage in completely filled tanks, the less expensive chrome-nickel steel is sufficient. 

The fennentor is filled with whole grapes under a blanket of carbon dioxide and kept at a moderate temperature (20-30°C) for 1-2 weeks. The atmosphere of the fermentor is then saturated with CO2 for 8-15 days. This is the pure carbonic maceration phase. Anaerobic metabolism reactions modify grape composition. Substances from the solid tissue disintegrated by anaerobio-sis are also diffnsed in the juice and the pulp. 

Anaerobiosis is generally effected in a hermetic fermentor, but grapes can also be wrapped in an airtight plastic tarpaulin and placed in a wooden crate. The crates filled with grapes at the vineyard are transported to the winery and stored. 

Anaerobiosis is obtained by filling an empty fermentor with carbon dioxide from an industrial gas cylinder or a fermenting tank. After filling, the carbon dioxide supply must be continued for 24-48 hours to compensate for possible losses and dissolution in the grape. After this period, fermentation emissions compensate for losses. The extinguishing of a candle flame when placed in the tank verifies anaerobiosis. 

Fermentors are filled with clarified juice. Approximately 10% of the tank volume is left empty to avoid the overflowing of foam (Section 3.2.5) produced during the tumultuous phase of alcoholic fermentation. 

Within the last 20 years or so, the use of active dry yeast (ADY) in winemaking has increased considerably. It has replaced the traditional practice of yeast starters in many wineries. In this formerly widespread method, a juice is strongly sulfited (10 g/hl) to eliminate spoilage yeasts and promote the growth of wine yeasts. It is then inoculated into newly filled fermentors at a concentration of 2-5% after several days of spontaneous fermentation. 

Carbon absorption utilizes activated carbon to physically absorb bioisoprene from the fermentor ofF-gas. As moisture would affect the absorption capacity of activated carbon, a dehumidifier unit is needed before the contact of the steam with activated carbon (Figure 16.5). The method is useful to recover the low concentration of bioisoprene at the laboratory level. Pioneering studies have shown that the method could absorb more than 80% of bioisoprene from the ofF-steam of 14-1 scale fermentation [52]. A preUminary study in our laboratory also confirmed that the absorption unit (filled with activated carbon fiber cloth) could effectively absorb gas-phase bioisoprene of low concentrations (1000-10 000 ppm, Zou et al., unpublished data). After the absorption step, an offline desorption/condensation step is needed to recover isoprene from activated carbon. Steam is utilized in the regeneration of the activated carbon and desorption of the isoprene. Then a series of condensers and cold traps follow to recover the liquid-phase isoprene. 

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