Temperature change over the length of heat exchangers might be an important factor affecting biofouling. This research aimed at assessing the impact of temperature on biofilm accumulation and composition with respect to bacterial community and extracellular polymeric substances. Two identical laboratory-scale plate heat exchanger modules were developed and tested. Tap water supplemented with nutrients was fed to the two modules to enhance biofilm formation. One “reference” module was kept at 20.0 ± 1.4 °C and one “heated” module was operated with a counter-flow hot water stream resulting in a bulk water gradient from 20 to 27 °C. Biofilms were grown during 40 days, sampled, and characterized using 16S rRNA gene amplicon sequencing, EPS extraction, FTIR, protein and polysaccharide quantifications. The experiments were performed in consecutive triplicate. Monitoring of heat transfer resistance in the heated module displayed a replicable biofilm growth profile. The module was shown suitable to study the impact of temperature on biofouling formation. Biofilm analyses revealed: (i) comparable amounts of biofilms and EPS yield in the reference and heated modules, (ii) a significantly different protein to polysaccharide ratio in the EPS of the reference (5.4 ± 1.0%) and heated modules (7.8 ± 2.1%), caused by a relatively lower extracellular sugar production at elevated temperatures, and (iii) a strong shift in bacterial community composition with increasing temperature. The outcomes of the study, therefore, suggest that heat induces a change in biofilm bacterial community members and EPS composition, which should be taken into consideration when investigating heat exchanger biofouling and cleaning strategies. Research potential and optimization of the heat exchanger modules are discussed.

Recently, increasing attention has been paid to the application of enzymes in a wide variety of leather production processes. The aim of the present study was to investigate the action of enzymatic pickling on derma’s collagen and the influence of this action on subsequent processes and properties of chromed and finished leather. The application of active in acidic medium proteolytic enzymes in the pickling process led to an additional impact on derma structure: collagen was more strongly affected and the porosity of the pelt dermis was reduced, but the hide became more thermally stable. The enzymatically pickled pelt bonded more chromium and reached higher shrinkage temperature while chroming; dyes penetrated deeper; such leather bonded more fatliquors. On the other hand, the action of enzymes worsened the physical–mechanical properties of the leather, as the experimental leather was weaker than the conventional one. The first was characterised by weaker grain layer and had significantly higher relative elongation. Therefore, as some properties improve and others worsen during such a process, the application of every enzyme should be carefully investigated and optimized to produce a leather with defined properties.

Due to their variety, specific activity, and mild reaction conditions, enzymes have a wide application in beam house processes such as soaking, dehairing, bating, and de-greasing. Recently, due to improvements in biotechnology, re-bating after chroming has received increased attention. The aim of this work was to investigate the application of enzyme preparation in the re-bating process and its effect on the semifinished and finished product, as well as its influence on post-tanning operations. The enzymatic treatment of chromed semifinished leather (wet blue) led to a higher shrinkage temperature (1–6 °C), greater water vapour absorption (0.3–5.5%), better chromium compounds exhaustion during re-chroming (4–21%), and better dye penetration. Moreover, collagen was affected during the enzymatic process; the results showed a greater concentration influence in the operation compared to the process time. On the other hand, no effect on the physical and mechanical properties and fat-liquoring process was observed. Overall, these results indicate that some properties and processes are improved; however, before use for re-bating, every enzyme should be carefully investigated.

Various methods of neutralisation of hide unhaired with sodium silicate and sodium sulphide have been investigated seeking to reduce or refuse ammonium sulphate conventionally applied for the neutralisation. Due to the high release of ammonia into the environment, alternative materials are being sought that do not impair the properties of the hide being processed and that a high-quality chromed semi-finished product of leather can be obtained. In the research, different methods of hide neutralisation and their influence on subsequent hide treatment processes qualitative indexes of the obtained leather were analysed and described. It has been found that after unhairing with sodium silicate and sodium sulphide hide, it is appropriate to neutralise and bate the hide by adding 1 % ammonium sulphate, 0.8 % lactic acid and 0.15 % proteolytic enzyme preparation OROPON ON2. To obtain the best quality of chromed semi-finished product of leather, it is advisable to pickle the hide using not more than 1 % sulfuric acid. In this way, neutralised-bated, pickled and chromed leather’s quality meets the quality requirements for chromed semi-finished product of leather.

The use of enzymes in leather processes has increased in recent years. Enzymes have gained more recognition because of their properties, such as specific activity, simple application, mild enzymatic reaction conditions, and non-polluting effluent generations. However, not all enzymatic operations are well investigated, and there is still a lack of knowledge on ferment usage in post-tanning processes. The aim of this study was to investigate the enzyme implementation in wet blue bating and its effect on semi-finished product. The various enzyme preparations were used for bating at different concentrations and process times. The amount of removed collagen proteins, the shrinkage temperature after bating and rechroming were assessed; on top of that, the amount of chrome compounds in semi-finished product and in the effluent was determined. The results showed that enzymatic bating had an effect on wet blue leather. The greatest difference was obtained using Zime SB enzyme preparation. The results obtained during the study are promising, even so, further research on mechanical properties, dying, and fatliquoring effects needs to be investigated to see enzymatic effect on the finished product.