Abstract
In the report, in order to determine which volatile compounds were produced by the fungus, the volatile organic compounds (VOCs) found in the GC-MS analyses of controls were removed from the list of VOCs appearing in the flask supporting fungal growth as done previously (Strobel et al., 2001). However, an examination of this approach has revealed that it was inaccurate for the study. The automated library search results generated from the NIST 2005 database spectral search were used as the only means of compound comparison between fungal products and those of the control. Due to the similarity of many alkane fragmentation patterns the automated search is not always reliable (Schulz & Dickschat, 2007). This difficulty in alkane identification was further complicated by a complex mixture of gases produced by NRRL 50072 that resulted in overlapping chromatographic peaks. The incomplete separation resulted in the automated library search algorithm (Agilent Chem Station Version C.0.0) returning different VOC assignments. This led to the incorrect conclusion that some compounds were in the fungal fermentation VOCs but not present in the controls. In addition to the automated library database search comparisons, manual inspection of retention times and fragmentation profiles for each chromatographic peak is necessary to accurately account for the media-derived VOCs. The data reported in the revised tables (below) reflect changes made after these additional aspects of the GC-MS data analyses were considered and these represent the most conservative estimates of the fungal VOC production. The temperature programme used for GC was as follows: 40 °C for 2 min, 10 °C min−1 ramp to 230 °C final temperature and a 5 min hold at 230 °C.
Therefore, as a result of these analytical difficulties, the VOCs in the tables in this Corrigendum primarily differ from those in the original paper by the absence of the branched- and long-chained alkanes. Since many of the VOCs made by this organism can serve as fuels or fuel additives, the term myco-diesel still applies, especially as it relates to the ability of this organism to produce a series of alkyl acetates, alcohols and acids representing some of the major straight-chained alkanes of diesel. Furthermore, the ability of the organism to digest cellulose and subsequently produce VOCs with fuel potential, while qualitatively different in the tables, is still notable. A more detailed and comprehensive study on the VOCs of this organism and a number of its close relatives is in this issue of Microbiology (Griffin et al., 2010). The overall conclusion is that the products of this organism following growth on a number of substrates have potential as fuels.
The authors would like to make the following corrections to the paper listed above.
Microbiology (2008), 154, part 11, 3319–3328.
The authors would like to note that technical errors occurred in the above report.
In the report, in order to determine which volatile compounds were produced by the fungus, the volatile organic compounds (VOCs) found in the GC-MS analyses of controls were removed from the list of VOCs appearing in the flask supporting fungal growth as done previously (Strobel et al., 2001). However, an examination of this approach has revealed that it was inaccurate for the study. The automated library search results generated from the NIST 2005 database spectral search were used as the only means of compound comparison between fungal products and those of the control. Due to the similarity of many alkane fragmentation patterns the automated search is not always reliable (Schulz & Dickschat, 2007). This difficulty in alkane identification was further complicated by a complex mixture of gases produced by NRRL 50072 that resulted in overlapping chromatographic peaks. The incomplete separation resulted in the automated library search algorithm (Agilent Chem Station Version C.0.0) returning different VOC assignments. This led to the incorrect conclusion that some compounds were in the fungal fermentation VOCs but not present in the controls. In addition to the automated library database search comparisons, manual inspection of retention times and fragmentation profiles for each chromatographic peak is necessary to accurately account for the media-derived VOCs. The data reported in the revised tables (below) reflect changes made after these additional aspects of the GC-MS data analyses were considered and these represent the most conservative estimates of the fungal VOC production. The temperature programme used for GC was as follows: 40 °C for 2 min, 10 °C min−1 ramp to 230 °C final temperature and a 5 min hold at 230 °C.
Therefore, as a result of these analytical difficulties, the VOCs in the tables in this Corrigendum primarily differ from those in the original paper by the absence of the branched- and long-chained alkanes. Since many of the VOCs made by this organism can serve as fuels or fuel additives, the term myco-diesel still applies, especially as it relates to the ability of this organism to produce a series of alkyl acetates, alcohols and acids representing some of the major straight-chained alkanes of diesel. Furthermore, the ability of the organism to digest cellulose and subsequently produce VOCs with fuel potential, while qualitatively different in the tables, is still notable. A more detailed and comprehensive study on the VOCs of this organism and a number of its close relatives is in this issue of Microbiology (Griffin et al., 2010). The overall conclusion is that the products of this organism following growth on a number of substrates have potential as fuels.
The authors would like to make the following corrections to the paper listed above.
1. Table 1, page 3322–3323
Table 1 is now replaced with a new Table 1⇓, as shown below. Please also note that the relative peak areas presented in this table are corrected values.
A GC-MS air space analysis of the volatile compounds produced by NRRL 50072 after an 18 day incubation under microaerophilic conditions at 23 °C on oatmeal agar
Compounds found in the control oatmeal agar bottle are not included in this table. Comparative GC-MS data with standard compounds are indicated in the footnotes under ‘Stds’. The total dry weight of the mycelial mat under these conditions was 38.9 mg.
2. Table 2, page 3325
Table 2 is now replaced with a new Table 2⇓, as shown below.
A GC-MS air space analysis of the volatile compounds produced by NRRL 50072 after an 18 day incubation under microaerophilic conditions at 23 °C on a cellulose-based medium
Compounds found in the control bottle are not included in this table. Comparative GC-MS data with standard compounds are indicated in the footnotes under ‘Stds’. The total dry weight of the mycelial mat under these conditions was 4.7 mg.
3. Table 3, page 3326
Table 3 is now replaced with a new Table 3⇓, as shown below.
A GC-MS air space analysis of the volatile compounds produced by NRRL 50072 after an 18 day incubation under microaerophilic conditions at 23 °C on host medium
Compounds found in the control bottle are not included in this table. Comparative GC-MS data/notes with standard compounds are indicated in the footnotes under ‘Stds’. The total dry weight of the mycelial mat under these conditions was 5.3 mg.