Fungi are widely exploited for large-scale production in the biotechnological industry to produce a diverse range of substances due to their versatility and relative ease of growing on various substrates. The occurrence of a phenomenon—the so-called fungal strain degeneration—leads to the spontaneous loss or decline of production capacity and results in an economic loss on a tremendous scale. Some of the most commonly applied genera of fungi in the biotechnical industry, such as Aspergillus, Trichoderma, and Penicillium, are threatened by this phenomenon. Although fungal degeneration has been known for almost a century, the phenomenon and its underlying mechanisms still need to be understood. The proposed mechanisms causing fungi to degenerate can be of genetic or epigenetic origin. Other factors, such as culture conditions, stress, or aging, were also reported to have an influence. This mini-review addresses the topic of fungal degeneration by describing examples of productivity losses in biotechnical processes using Aspergillus niger, Aspergillus oryzae, Trichoderma reesei, and Penicillium chrysogenum. Further, potential reasons, circumvention, and prevention methods are discussed. This is the first mini-review which provides a comprehensive overview on this phenomenon in biotechnologically used fungi, and it also includes a collection of strategies that can be useful to minimize economic losses which can arise from strain degeneration.
Key points
• Spontaneous loss of productivity is evident in many fungi used in biotechnology.
• The properties and mechanisms underlying this phenomenon are very versatile.
• Only studying these underlying mechanisms enables the design of a tailored solution.
A distillation method is described for the determination of water in bleaching powder and high-test calcium hypochlorites, involving heating the sample with o-dichlorobenzene to drive all the water into the graduated separator tube of a specially constructed one-piece apparatus. THE water content of bleaching powder, which is used for bleaching, disinfection, and decontamination, is an important factor in its stability (7, 8). Of lesser importance is its contribution to corrosion in containers and to caking in cold weather.This applies to bleaching powder made by the chamber or rotary processes and to the high-test calcium hypochlorites. For these reasons, knowledge of the water content is particularly desirable to users of bleaching powder for procurement and specification purposes.A variety of methods have been tried for the determination of water in bleaching powder, such as by heating the powder quickly in a tube at 200°to 250°and absorbing the liberated chlorine in potassium iodide solution (9), by difference between 100% and the total percentages of calcium hypochlorite, calcium chloride, sodium chloride (if present), calcium hydroxide, calcium carbonate, calcium sulfate, and insolubles in acid, and by passing
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