To characterize the silage and, con

To characterize the silage and, consequently the action
of the inoculants, many characteristics of the silage
should be assessed. The silage with the lowest loss of
DM had a lower ethanol concentration than silages
with higher DM losses. The strains that resulted in
the greatest loss of DM presented the highest amount
of lactic acid. In this silage, homofermentative strains
may have been dominant.
The silage inoculated with the UFLA SIL51 and
UFLA SIL52 strains had lower concentrations of ethanol
than the silage inoculated with other strains (Table
5). However, the yeast population was similar to that
found in the control silage. Ávila et al. (2010a) identified
yeast species during sugar cane silage and reported
that different yeasts species had different abilities to
produce ethanol. In the current study, the yeast species
were not identified. Thus, despite the similarities
between the yeast populations in silage inoculated with
UFLA SIL51 and UFLA SIL52 strains and the control
silage, they can be variable, resulting in the production
of a different amount of ethanol. Similar results were
also found by Carvalho et al. (2012).
The silage inoculated with UFLA SIL51 and UFLA
SIL52 showed higher concentrations of acetic acid and
1,2-propanediol compared with the silage inoculated
with the other LAB strains. Acetic acid is a weak acid
in an environment with a pH lower than its acid dissociation
constant (pKa; 4.73). At this pH, the acid
remains in its undissociated form and enters the cell
of the microorganism. Once inside the cell, the acid
is dissociated and releases H+ ions, which reduces the
intracellular pH. To increase the pH again, the microorganism
must expel the H+ ions by an active transport
process, which requires energy, thus delaying growth
and potentially causing the death of the cell (Davidson,
2007). Other studies have reported that silages with
higher concentrations of acetic acid have lower yeast
counts (Driehuis et al., 2001; Filya et al., 2006).
1,2-Propanediol can be produced by some LAB,
such as Lb. buchneri and Lb. brevis, from lactic acid.
However, in the present study, the amounts of 1,2-pro-panediol were much higher in the silage inoculated with
Lb. hilgardii, which has a similar metabolism to that of
Lb. buchneri and Lb. brevis. Thus, Lb. hilgardii might
also produce 1,2-propanediol from lactic acid. It was
not clear whether Lb. diolivorans converted the 1,2-propanediol
into propionic acid because the propionic acid
levels were variable and showed no correlation with
those of 1,2-propanediol in the current study. Somehow,
these microorganisms were the main contributors to the
quality of the sugar cane fermentation, which seems to
be determined by the production of acetic acid.
Concentrations of butyric acid were variable and
were lower than 5 g/kg of DM for all silages. Sugar cane
silage generally has a lower butyric acid concentrations
because of its low pH value, which is usually below 3.5
(Amaral et al., 2009; Zopollato et al., 2009). The effect
of inoculants containing different strains on the butyric
acid concentration of the silage varied, but silage inoculated
with UFLA SIL19, UFLA SIL42, UFLA SIL46,
UFLA SIL51, or UFLA SIL52 had lower concentrations
of butyric acid than silages inoculated with the other
strains. Carvalho et al. (2012) found a reduction in the
butyric acid concentration in sugar cane silage from 7.7
to 5.0 g/kg within 60 d of fermentation. However, after
170 d of fermentation, the butyric acid concentration in
the silage inoculated with Lb. buchneri increased from
4.0 to 12.0 g/kg.
Data regarding the aerobic stability of silage, which
was measured by temperature fluctuations, showed
similarities in the silages inoculated with different LAB
strains. The lack of a significant effect can be explained
by the high variation in the results. In the present study,
the time over which silage remained stable was less (24
h) than that found by Ávila et al. (2009; 33 and 60h).
The strains that provided better silage characteristics,
such as a smaller yeast populations, lower ethanol
content, and less DM loss, were selected based on their
high production of acetic or propionic acids. These data
confirmed that facultative heterofermentative strains
are not good candidates as inoculants for sugar cane silage
and may even decrease silage quality by increasing
DM losses throughout the fermentative process. The
strains that produced acetic or propionic acids in addition
to lactic acid were the most suitable for this type
of silage because acetic and propionic acids are more
effective in inhibiting yeast, which causes the greatest
problems during sugar cane ensilage. Strains UFLA
SIL51 and UFLA SIL52 were the most promising in
reducing DM losses, as well as being the strains that
resulted in a smaller yeast populations, lesser ethanol
production, a greater population of LAB, and lower
concentration of butyric acid. The greater production
of acetic acid and 1,2-propanediol may have inhibited
the metabolism of yeast during the anaerobic fermentation
of the silage, resulting in lower DM losses. This
effect, however, was not observed after the opening
of the silos. Reduction of DM loss is the main objective
when LAB inoculants are used in silage, because
losses during anaerobic fermentation are greater than
those during the aerobic phase of the sugar cane silage.
Therefore, Lb. hilgardii was suitable for use in sugar
cane silage and should be evaluated in other cultures.
CONCLUSIONS
Preselection of bacterial strains for sugar cane silage
in the laboratory is useful when a large number of microorganisms
must be assessed. In general, obligatory
heterofermentative strains showed better results than
facultative heterofermentative strains, in terms of DM
loss, in the anaerobic phase of silage fermentation. The
strains UFLA SIL51 and UFLA SIL52, identified as Lb.
hilgardii, were the most promising.
ACKNOWLEDGMENTS
The authors thank Conselho Nacional de Desenvolvimento
Científico e Tecnológico do Brasil (CNPQ),
Fundação de Amparo a Pesquisa de Minas Gerais
(FAPEMIG, Brazil), Coordenação de Aperfeiçoamento
de Pessoal de Nível Superior(CAPES, Brazil), and Lallemand
Animal Nutrition SAS (Milwaukee, WI) for
financial support and scholarship.

Hasil (Bahasa Indonesia) 1:

Untuk menandai silase dan, akibatnya tindakanpola, banyak karakteristik silaseharus dinilai. Silase dengan hilangnya terendahDM memiliki etanol konsentrasi yang lebih rendah daripada silagesdengan tinggi DM kerugian. Strain yang mengakibatkankerugian terbesar DM disajikan jumlah tertinggiasam laktat. Di silase ini, strain homofermentatifmungkin telah dominan.Silase diinokulasi dengan UFLA SIL51 danUFLA SIL52 strain memiliki konsentrasi yang lebih rendah etanoldaripada silase diinokulasi dengan strain lainnya (tabel5). Namun, populasi jamur ini sama denganditemukan di kontrol silase. Ávila et al. (2010a) yang diidentifikasispesies ragi selama gula tebu silase dan dilaporkanbahwa spesies ragi yang berbeda memiliki kemampuan yang berbeda untukmenghasilkan etanol. Dalam studi saat ini, spesies ragiyang tidak diidentifikasi. Dengan demikian, meskipun kesamaanantara ragi populasi di silase diinokulasi denganUFLA SIL51 dan UFLA SIL52 strain dan kontrolsilase, mereka dapat menjadi variabel, mengakibatkan produksidalam jumlah yang berbeda etanol. Hasilnya samajuga ditemukan oleh Carvalho et al. (2012).Silase diinokulasi dengan UFLA SIL51 dan UFLASIL52 menunjukkan konsentrasi yang lebih tinggi dari asam asetat dandibandingkan dengan silase diinokulasi 1,2-propanedioldengan alunan laboratorium lainnya. Asam asetat adalah asam lemahdi lingkungan dengan pH lebih rendah daripada yang disosiasi asamkonstan (pKa; 4,73). Pada pH ini, asamtetap dalam bentuk undissociated dan memasuki selmikroorganisme. Sekali di dalam sel, asamadalah terpisahkan dan melepaskan H + ion, yang mengurangipH intraselular. Untuk meningkatkan pH lagi, mikroorganismeharus mengusir ion H + yang oleh transpor aktifproses yang memerlukan energi, dengan demikian menunda pertumbuhandan berpotensi menyebabkan kematian sel (Davidson,2007). studi lain telah melaporkan bahwa silages dengankonsentrasi yang lebih tinggi dari asam asetat memiliki lebih rendah ragimenghitung (Driehuis et al., 2001; Filya et al., 2006).1,2-Propanediol dapat diproduksi oleh beberapa laboratorium,seperti Lb. buchneri dan Lb. brevis, dari asam laktat.Namun, dalam penelitian ini, jumlah 1,2-pro-panediol yang lebih tinggi di silase diinokulasi denganLb. hilgardii, yang memiliki serupa metabolisme yangLb. buchneri dan Lb. brevis. Dengan demikian, mungkin Lb. hilgardiijuga memproduksi 1,2-propanediol dari asam laktat. Itutidak jelas apakah Lb. diolivorans dikonversi 1,2-propanediolmenjadi asam propionat karena asam propionattingkat adalah variabel dan menunjukkan tidak ada korelasi denganorang-orang dari 1,2-propanediol dalam penelitian ini. Entah bagaimana,mikroorganisme ini merupakan kontributor utamakualitas fermentasi gula tebu, yang tampaknyaditentukan oleh produksi asam asetat.Butyric acid adalah variabel danlebih rendah dari 5 g/kg DM untuk semua silages. Tebusilase umumnya memiliki konsentrasi asam butirat yang lebih rendahkarena nilai pH rendah, yang biasanya di bawah 3,5(Amaral et al., 2009; Zopollato et al., 2009). Efekpola yang mengandung strain yang berbeda pada butiratkonsentrasi asam silase bervariasi, tetapi silase diinokulasidengan UFLA SIL19, UFLA SIL42, UFLA SIL46,UFLA SIL51, atau UFLA SIL52 memiliki konsentrasi yang lebih rendahasam butirat daripada silages diinokulasi dengan yang lainstrain. Carvalho et al. (2012) menemukan pengurangankonsentrasi asam butirat dalam silase tebu dari 7,75.0 g/kg dalam 60 d fermentasi. Namun, setelahHotel-d 170 fermentasi, konsentrasi asam butirat disilase diinokulasi dengan Lb. buchneri meningkat dari4.0 untuk 12,0 g/kg.Data mengenai stabilitas aerobik silase, yangdiukur oleh fluktuasi suhu, menunjukkankesamaan dalam silages diinokulasi dengan laboratorium yang berbedastrain. Kurangnya efek signifikan dapat dijelaskanvariasi tinggi dalam hasil. Dalam penelitian ini,waktu selama silase yang tetap stabil adalah kurang (24h) daripada yang ditemukan oleh Ávila et al. (2009; 33 dan 60 h).Strain yang diberikan lebih baik silase karakteristikseperti populasi ragi yang lebih kecil, lebih rendah etanolkonten, dan kurang kehilangan DM, dipilih berdasarkan merekaTingginya produksi asetat atau asam propionat. Data inimenegaskan bahwa Heterofermentatif fakultatif straintidak kandidat yang baik sebagai inokulan untuk silase tebudan mungkin bahkan menurunkan silase kualitas dengan meningkatkanDM kerugian seluruh proses fermentasi. Thestrain yang dihasilkan asetat atau asam propionat Selainasam laktat adalah yang paling cocok untuk jenis inidari silase karena asetat dan asam propionat lebihefektif dalam menghambat ragi, yang menyebabkan terbesarmasalah selama ensilage gula tebu. Strain UFLASIL51 dan UFLA SIL52 adalah yang paling menjanjikan dimengurangi kerugian DM, serta menjadi galur yangmengakibatkan populasi ragi yang lebih kecil, lebih rendah etanolproduksi, populasi lebih besar dari LAB, dan lebih rendahkonsentrasi asam butirat. Produksi yang lebih besarasam asetat dan 1,2-propanediol mungkin telah menghambatmetabolisme ragi selama fermentasi anaerobdari silase, mengakibatkan kerugian DM yang lebih rendah. IniEfek, bagaimanapun, tidak diamati setelah pembukaandari Silo. Pengurangan hilangnya DM adalah tujuan utamaKetika LAB inokulan yang digunakan dalam silase, karenakerugian selama fermentasi anaerob lebih besar darimereka selama fase aerobik silase tebu.Oleh karena itu, Lb. hilgardii sangat cocok digunakan pada gulatebu silase dan harus dievaluasi dalam budaya lain.KESIMPULANBakteri strain untuk silase tebu yang dinginkandi laboratorium adalah berguna ketika sejumlah besar dari mikroorganismeharus dinilai. Secara umum, wajibHeterofermentatif strain menunjukkan hasil yang lebih baik daripadaHeterofermentatif fakultatif strain, dalam hal DMkerugian, dalam tahap anaerobik silase fermentasi. Thestrain UFLA SIL51 dan SIL52 UFLA, diidentifikasi sebagai Lb.hilgardii, adalah yang paling menjanjikan.UCAPAN TERIMA KASIHPara penulis terima Conselho Nacional de DesenvolvimentoCientífico e Institut lakukan Brasil (CNPQ),Fundação de Amparo Pesquisa de Minas Gerais(FAPEMIG, Brasil), Coordenação de Aperfeiçoamentode Pessoal de Nível Superior (MANTEL, Brasil), dan LallemandHewani SAS (Milwaukee, WI) untukBeasiswa dan dukungan keuangan.