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Purification is a critical step to obtain hydrophobin HFBII for use in positive applications. In this study, hydrophobin HFBII was produced by Trichoderma reesei via submerged fermentation. Using the CO2-foam fractionation method yielded a fourfold increase in protein concentration. The foamate (αL-HFBII) was dried using a nano spray-dryer under optimal temperature. The gushing activity of the dried foamate (αS-HFBII) decreased. Addition of Tween 80 to the foamate before the drying process partially prevented the deactivation of hydrophobin HFBII. The purity of the powder was enhanced based on the theory of CO2-nanobubbles in a CO2-rich environment. The collected CO2-nanobubbles were added to an apolar–polar system and the interface of these two phases was collected. After evaporation of the apolar phase, the purity of the hydrophobins assembled on the surface of the liquid was significantly improved.

Gushing has been recognized as a disastrous phenomenon for contaminated carbonated beverages. Recent advances highlighted the ability of the class II hydrophobin films to interact via the hydrophob...

The presence of Class II hydrophobins produced by fungi on barley results in primary gushing of beer. Gushing is the spontaneous overfoaming of carbonated beverages by opening of bottles. Solving gushing problems caused by brewing raw materials has received much scientific attention. Lipophilic extract of hops are introduced to brewers as foam suppressor in fermenters. We studied the effects of hop extract on gushing and found that lipophilic hop extract could reduce gushing. The effects are different when hop extract is added before mashing than when it is added after mashing. Hop extract contains fats and waxes and the effects on gushing are explained by a change in the physical state of its components during mashing which are due to temperature effects. Especially the effect of saturated fatty acids and waxes becomes apparent which are known as gushing inducers. This indicates that with respect to gushing potential of the hop extract's components, it is better to be added to cold wort (after mashing and filtration). Our study also showed an important effect of the filtration step on the amount of gushing.

When weather conditions are damp, barley crops can be infected by fungi that produce amphiphilic proteins called hydrophobins. We postulated that these hydrophobins contaminate CO2 bubbles during b...

Agar contact microbiological sampling techniques, based on a transfer of the microorganisms present on a surface to a culture medium, are widely used to assess and control surface cleanliness and to evaluate microbial contamination levels. The effectiveness of these techniques depends on many environmental parameters that influence the strength of attachment of the bacteria to the surface. In the present study, stainless steel and high density polyethylene surfaces were inoculated with known concentrations of Staphylococcus epidermidis. Following an experimental design, the surfaces were sampled with different types of replicate organism direct agar contact plates and Petrifilm; results indicated that recovery rates were influenced by the presence of egg white albumin or Tween 80 in the inoculum solutions or by the introduction of surfactants into the contact agar of the microbiological sampling techniques. The techniques yielded significantly different results, depending on sampling conditions, underlining the need for a standardization of laboratory experiments to allow relevant comparisons of such techniques.

J. Am. Soc. Brew. Chem. 72(1):12-21, 2014 Gushing is the vigorous overfoaming of carbonated beverages when the bottle is opened. Primary gushing in beer is mostly caused by a group of proteins called hydrophobins secreted by filamentous fungi, which contaminate CO2 gaseous molecules during carbonation and form nanobubbles. The influence of hop oil antifoam on primary gushing showed a complete suppressing effect in sparkling water, a decreasing effect in wort, and no influence on gushing-positive beers. This shows the importance of the critical point of addition of this product in the brewing process. GC and GC-MS analysis show that commercial available lipophilic hop extract comprises fatty acids, either saturated fatty acids (SFA) or unsaturated fatty acids (UFA) (both free and incorporated in mono-, di-, and triglycerides), waxes (long-chain alkanes), and steroid compounds. Gushing analysis of each compound showed that SFA and UFA behave in a different manner regarding gushing. In contrast to SFA and trans-form UFA, cis-form UFAs do not induce gushing. Long-chain alkanes provide sufficient hydrophobic structures to interact with gaseous CO2 molecules and induce gushing. Because hop antifoam molecules are hydrophobic, they interact with hydrophobins and prevent interaction with CO2 and, consequently, inhibit the possibilities of development of the explosive nanobubble structure.

A spontaneous, wild, and uncontrolled liquid expulsion immediately upon opening non-shaken bottles of carbonated beverages defines primary gushing. The liquid volume resulting from primary gushing differs greatly even in the same laboratory. A thermodynamic investigation of the process can determine parameters responsible for this phenomenon. Although the required energy to provoke gushing is believed to be obtained mostly by the expansion of the nanobubbles, there are many other sources that might be significantly involved in this case. Providing the required energy via the explosion of the nanobombs breaks the weak hydrogen bond between CO 2 and water molecules and results in the release of the CO 2 . In this study, the authors claim that primary gushing is mainly linked to the CO 2 properties and consequently related to the liquid temperature at bottle opening (K), the pressure (bar), the CO 2 concentration (g/L), and the energy (N.m). © 2013 American Society of Brewing Chemists, Inc. ispartof: JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS vol:71 issue:3 pages:149-152 status: published

Although there is a common agreement that hydrophobins and CO2 are responsible for primary gushing of carbonated beverages, the bio-molecular mechanism of this phenomenon is not well understood. Here, hydrophobin HFBII has been produced, extracted, and purified. A gushing test and DLS analysis was performed and allowed the authors to design an MD simulation setup to investigate the interaction of CO2 molecules with HFBII in time. The results indicate that CO2 molecules tend to aggregate at the hydrophobic patch of HFBII twice as much as to the rest of the protein. A model is proposed that elucidates the "nanobomb" formation depicting a definite chemical and biophysical description of the primary gushing mechanism. © 2012 American Society of Brewing Chemists, Inc. ispartof: JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS vol:70 issue:4 pages:249-256 status: published