Biorefineries using waste – production of energy and chemicals from biomasses by micro-organisms - Biomass as Energy Source: Resources, Systems and Applications - page 249

0.6

0.5

0.4

MOS1 _Channel max

0.3

MOS2_Channel max

0.2

MOS3_Channel max

ScCell 1_Channel max

0.1

ScCell2_Channel max

0

Figure 13.5a. Experiment carried out with circulated car washing liquid/water using microaerophilic gas
flow in PMEUScentrion®. Syringe 1: sludge withTYG(1:10), gas mixture 2/3 N 2 and 1/3 air.
The curves indicate the emissions as detected with different metal oxide sensors (MOS) and
Semi-conductor Cells (ScCell). Major microbial breakdown activities were provoked for five
hours in this experiment.

of biocatalyst is the most useful for any particular application. Bacterial or mold strains could be
used for the production of hydrolytic enzymes in the process fluid or in a pretreatment unit, or
alternatively they could be replaced with their enzymes. Nowadays, promising results have been
obtained with the so-called consolidated bioprocesses (CBP).

13.8.5 Mixed cultures in bioengineering
Microbiological research is largely based on isolated pure cultures. However, in many cases
the microbes form integrated communities in which some species act in balanced, or even
in a symbiotic fashion. For example, the various types of the small intestinal bacteria, the
mixed acid fermenting strains such as E. coli and the more neutral substances producing
Klebsiella / Enterobacter group are maintaining the duodenal pH at 6 (Hakalehto et al. , 2008).
This dualistic balance was established in simulation with the PMEU, where the acids produced
by E. coli were neutralized with the 2,3-butanediol fermentation of Klebsiella mobilis . The two
types of the facultatives were shown to produce equal growth yields in mixed culture and in two
separate pure cultures. The strains were shown to establish the balance in almost all cases, and
this balance was not shaken by other intruding species (Hakalehto et al. , 2010). The dualistic
balance between E. coli and klebsiellas is one example of the powerful means offered by the
mixed cultures in industrial biotechnology.

13.8.6 Novel principles for the planning of unit operations for bulk production
In the case of almost any organic biomass, the material itself is containing mixed cultures of
various microorganisms. We were studying by the PMEU cultivation method for the circulated car
washing water-based solution containing organic substances. When the sterile air flow (aerobic
condition) was used for cultivation experiments in the PMEU Scentrion® device, the natural
microbial population generated a continuous gas flow (Fig.13.5). The detected emission could
partially derive from the washing liquids and the dirt components dissolved or suspended into the
fluids. An addition of 1:10 or 1:100 ofTYGmedium (Tryptone,Yeast Extract, Glucose) was added
to boost the microbial growth. However, if laboratory strain of Klebsiella mobilis was inoculated
into either of the supplemented washing liquids, the emissions of the volatiles peaked quicker
than with the natural microbial population. The effect was more readily evoked with sterile air
than with the microaerobic gas flow. The results indicate that the naturally developed microbial